Mechanical enhancement of dense and porous organosilicate materials by UV exposure

ABSTRACT

Low dielectric materials and films comprising same have been identified for improved performance when used as interlevel dielectrics in integrated circuits as well as methods for making same. In one aspect of the present invention, an organosilicate glass film is exposed to an ultraviolet light source wherein the film after exposure has an at least 10% or greater improvement in its mechanical properties (i.e., material hardness and elastic modulus) compared to the as-deposited film.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/379,466, filed 4 Mar. 2003, the disclosure ofwhich is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the formation ofdielectric films. More specifically, the invention relates to dielectricmaterials and films comprising same having a low dielectric constant andenhanced mechanical properties and methods for making same.

[0003] There is a continuing desire in the microelectronics industry toincrease the circuit density in multilevel integrated circuit devicessuch as memory and logic chips to improve the operating speed and reducepower consumption. In order to continue to reduce the size of devices onintegrated circuits, the requirements for preventing capacitivecrosstalk between the different levels of metallization becomesincreasingly important. These requirements can be summarized by theexpression “RC”, whereby “R” is the resistance of the conductive lineand “C” is the capacitance of the insulating dielectric interlayer.Capacitance “C” is inversely proportional to line spacing andproportional to the dielectric constant (k) of the interlayer dielectric(ILD). Such low dielectric materials are desirable for use, for example,as premetal dielectric layers or interlevel dielectric layers.

[0004] A number of processes have been used for preparing low dielectricconstant films. Chemical vapor deposition (CVD) and spin-on dielectric(SOD) processes are typically used to prepare thin films of insulatinglayers. Other hybrid processes are also known such as CVD of liquidpolymer precursors and transport polymerization CVD. A wide variety oflow K materials deposited by these techniques have been generallyclassified in categories such as purely inorganic materials, ceramicmaterials, silica-based materials, purely organic materials, orinorganic-organic hybrids. Likewise, a variety of processes have beenused for curing these materials to, for example, decompose and/or removevolatile components and substantially crosslink the films, such asheating, treating the materials with plasmas, electron beams, or UVradiation.

[0005] The industry has attempted to produce silica-based materials withlower dielectric constants by incorporating organics or other materialswithin the silicate lattice. Undoped silica glass (SiO2), referred toherein as “USG”, exhibits a dielectric constant of approximately 4.0.However, the dielectric constant of silica glass can be lowered to avalue ranging from 2.7 to 3.5 by incorporating terminal groups such asfluorine or methyl into the silicate lattice. These materials aretypically deposited as dense films and integrated within the IC deviceusing process steps similar to those for forming USG films.

[0006] An alternative approach to reducing the dielectric constant of amaterial may be to introduce porosity, i.e., reducing the density of thematerial. A dielectric film when made porous may exhibit lowerdielectric constants compared to a relatively denser film. Porosity hasbeen introduced in low dielectric materials through a variety ofdifferent means. For example, porosity may be introduced by decomposingpart of the film resulting in a film having pores and a lower density.Additional fabrication steps may be required for producing porous filmsthat ultimately add both time and energy to the fabrication process.Minimizing the time and energy required for fabrication of these filmsis desirable; thus discovering materials that can be processed easily,or alternative processes that minimize processing time, is highlyadvantageous.

[0007] The dielectric constant (κ) of a material generally cannot bereduced without a subsequent reduction in the mechanical properties,i.e., elastic modulus (Young's modulus), hardness, toughness, of thematerial. Mechanical strength is needed for subsequent processing stepssuch as etching, CMP (“Chemical Mechanical Planarization”), anddepositing additional layers such as diffusion barriers for copper,copper metal (“Cu”), and cap layers on the product. Mechanicalintegrity, or stiffness, compressive, and shear strengths, may beparticularly important to survive CMP. It has been found that theability to survive CMP may be correlated with the elastic modulus of thematerial, along with other factors including polishing parameters suchas the down force and platen speed. See, for example, Wang et al.,“Advanced processing: CMP of Cu/low-κ and Cu/ultralow-κ layers”, SolidState Technology, September, 2001; Lin et al., “Low-k DielectricsCharacterization for Damascene Integration”, International InterconnectTechnology Conference, Burlingame, Calif., June, 2001. These mechanicalproperties are also important in the packaging of the final product.Because of the trade-off in mechanical properties, it may be impracticalto use certain porous low dielectric compositions.

[0008] Besides mechanical properties, an additional concern in theproduction of a low dielectric film may be the overall thermal budgetfor manufacture of the IC device. The method used extensively in theliterature for cross-linking a low dielectric film and/or introducingporosity into a film is thermal annealing. In the annealing step, or acuring step, the film is typically heated to decompose and/or removevolatile components and substantially cross-link the film.Unfortunately, due to thermal budget concerns, various components of ICdevices such as Cu metal lines can only be subjected to processingtemperatures for short time periods before their performancedeteriorates due to undesirable diffusion processes. Additional heatingand cooling steps also can significantly increase the overallmanufacturing time for the device, thereby lowering the throughput.

[0009] An alternative to the thermal anneal or curing step is the use ofultraviolet (“UV”) light in combination with an oxygen-containingatmosphere to create pores within the material and lower the dielectricconstant. The references, Hozumi, A. et al. “Low Temperature Eliminationof Organic Components from Mesostructured Organic-Inorganic CompositeFilms Using Vacuum Ultraviolet Light”, Chem. Mater. 2000 Vol. 12, pp.3842-47 (“Hozumi I”) and Hozumi, A et al., “Micropattterned Silica Filmswith Ordered Nanopores Fabricated through Photocalcination”, NanoLetters2001, 1(8), pp. 395-399 (“Hozumi II”), describe removing acetyltrimethylammonium chloride (CTAC) pore-former from atetraethoxysilane (TEOS) film using ultraviolet (“VUV”) light (172 nm)in the presence of oxygen. The reference, Ouyang, M., “Conversion ofSome Siloxane Polymers to Silicon Oxide by UV/Ozone PhotochemicalProcesses”, Chem. Mater. 2000, 12(6), pp. 1591-96, describes using UVlight ranging from 185 to 254 nm to generate ozone in situ to oxidizecarbon side groups within poly(siloxane) films and form a SiO₂ film. Thereference, Clark, T., et al., “A New Preparation of UV-Ozone Treatmentin the Preparation of Substrate-Supported Mesoporous Thin Films”, Chem.Mater. 2000, 12(12), pp. 3879-3884, describes using UV light with awavelength below 245.4 nm to produce ozone and atomic oxygen to removeorganic species within a TEOS film. These techniques, unfortunately, maydamage the resultant film by chemically modifying the bonds that remainwithin the material. For example, exposure of these materials to anoxidizing atmosphere can result in the oxidation of the C atomscontained therein which has an adverse effect on the dielectricproperties of the material.

[0010] U.S. Pat. No. 4,603,168 describes cross-linking analkenyl-organopolysiloxane or organohydrosiloxane film by exposure to UVlight or electron beam radiation in the presence of heat. The filmfurther includes a dopant such as a photosensitizer like benzophenone ora platinum catalyst that is present in small concentrations to initiateand catalyze the cross-linking. Likewise, the reference Guo, et al.,“Highly Active Visible-light Photocatalysts for Curing CeramicPrecursor”, Chem. Mater. 1998, 10(2), pp. 531-36, describes using aplatinum bis(beta-diketonate) catalyst to cross-linkoligo(methylsilylene)methylene and tetravinylsinlane using UV/visiblelight. The presence of metal catalysts and chromophores would beunsuitable in dielectric films.

[0011] U.S. Pat. No. 6,284,500 describes using UV light in the 230 to350 nm wavelength range to photoinitiate cross-linking within an organicpolymer film formed by CVD or an organosilsiquoxane film formed byspin-on deposition to improve the adhesion and mechanical properties ofthe film. The '500 patent teaches that a thermal annealing step may beused to stabilize the cross-linked film.

[0012] Published U.S. patent application No. 2003/054115 (the '115application) teaches UV curing a porous dielectric material produced byCVD or spin-on deposition methods to produce a UV-cured porousdielectric material having an improved modulus and comparable dielectricconstant. The '115 application demonstrates that UV exposure in an O₂atmosphere is more effective than UV exposure in a N₂ atmosphere.However, the '115 application also teaches that the UV cure can generatea notable amount of polar species in the porous dielectric materials.Further, the '115 application states that “in all cases a subsequent orpossibly concomitant anneal step is necessary in order to remove theSi—OH bonds which are typically generated during the UV curing process.”

[0013] U.S. Pat. No. 6,566,278 teaches densifying a carbon-doped,silicon oxide (SiC_(x)O_(y)) film by exposing the film to UV radiation.The carbon-doped silicon oxide film is deposited via chemical vapordeposition of an oxygen-supplying gas and an organosilane siliconsupplying gas. The film is then exposed to UV radiation generated froman excited gas species such as xenon, mercury, deuterium, or KrCl₂.

[0014] U.S. Pat. Nos. 5,970,384 and 6,168,980 describe exposing a PVD orCVD deposited oxide gate layer to UV light in the presence of N2O, NH3,or N2H4 at temperatures between 300 and 700° C. The methods described inboth the '384 and '980 patents reduce the C and H impurities within theoxide gate layer and introduce nitrogen near the boundary of thematerial with the silicon substrate.

[0015] Accordingly, there is a need in the art to provide improveddielectric materials having low dielectric constant and sufficientmechanical strength and a method and mixture for making same. Due tothermal budget concerns, there is an additional need for a lowtemperature treatment for the production low dielectric constantmaterials for integrated circuits.

[0016] All references cited herein are incorporated herein by referencein their entirety.

BRIEF SUMMARY OF THE INVENTION

[0017] The present invention satisfies one, if not all, of the needs ofthe art by providing a process for improving the mechanical propertiesof an organosilicate glass film. Specifically, in one aspect of thepresent invention, there is provided a process for improving thematerial hardness and elastic modulus of an organosilicate filmcomprising: to provide the organosilicate film having a first materialhardness and a first elastic modulus; and exposing the organosilicatefilm to an ultraviolet radiation source within a non-oxidizingatmosphere to provide the organosilicate film having a second materialhardness and a second elastic modulus wherein the second materialhardness and the second elastic modulus are at least 10% higher than thefirst material hardness and the first elastic modulus.

[0018] In another aspect of the present invention, there is provided achemical vapor deposition process for making an organosilicate glassfilm having the formula Si_(v)O_(w)C_(x)H_(y)F_(z), wherev+w+x+y+z=100%, v is from 10 to 35 atomic %, w is from 10 to 65 atomic%, x is from 5 to 30 atomic %, y is from 10 to 50 atomic %, and z isfrom 0 to 15 atomic % comprising: providing a substrate within a vacuumchamber; introducing at least one chemical reagent comprising astructure-former precursor selected from the group consisting of anorganosilane and an organosiloxane and a pore-former precursor into thevacuum chamber; applying energy to the at least one chemical reagent inthe vacuum chamber to induce reaction of the reagent to deposit anorganosilicate film on at least a portion of the substrate; and exposingthe organosilicate film to an ultraviolet light source within anon-oxidizing atmosphere wherein the material hardness and the elasticmodulus of the organosilicate material after the exposing step arehigher than the material hardness and the elastic modulus of theorganosilicate material before the exposing step and wherein theorganosilicate material is substantially free of Si—OH bonds.

[0019] In yet another aspect of the present invention, there is provideda mixture for depositing an organosilicate film, the mixture comprisingat least one structure-former precursor selected from the groupconsisting of an organosilane and an organosiloxane wherein the at leastone structure-former precursor and/or the organosilicate film exhibitsan absorbance in the 200 to 400 wavelength range.

[0020] In an additional aspect of the present invention, there isprovided a mixture for depositing an organosilicate film comprising from5 to 95% of a structure-former precursor selected from the groupconsisting of an organosilane and an organosiloxane and from 5 to 95% ofa pore-former precursor wherein at least one of the precursors and/orthe organosilicate film exhibits an absorbance in the 200 to 400 nmwavelength range.

[0021] In a still further aspect of the present invention, there isprovided a process for preparing a porous organosilicate film having adielectric constant of 2.7 or less comprising: forming a composite filmcomprising a structure-former material and a pore-former materialwherein the composite film has a first dielectric constant, a firsthardness, and a first material modulus; and exposing the composite filmto at least one ultraviolet light source within a non-oxidizingatmosphere to remove at least a portion of the pore-former materialcontained therein and provide the porous organosilicate film wherein theporous organosilicate film has a second dielectric constant, a secondhardness, and a second material modulus and wherein the seconddielectric constant is at least 5% less than the first dielectricconstant, the second modulus is at least 10% greater than the firstmodulus, and the second hardness is at least 10% greater than that ofthe first hardness.

[0022] These and other aspects of the invention will become apparentfrom the following detailed description.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[0023]FIGS. 1a through 1 c provides an illustration of the various stepsof one embodiment of the present invention wherein the exposure to an UVradiation energy source results in the formation of pores within thefilm.

[0024]FIG. 2 compares the relationship between hardness and dielectricconstant for as-deposited, thermally annealed, and UV exposed dense OSGglass films, deposited using a DEMS structure-former precursor atvarious processing temperatures.

[0025]FIG. 3 provides the IR absorption spectrum for an as-deposited,thermally annealed, and UV exposed porous OSG glass film deposited usinga MEDS structure-former precursor and an ATRP pore-former precursor.

[0026]FIG. 4 provides the UV/V absorption spectrum of the as-depositedporous OSG glass film deposited using a DEMS structure-former precursorand an ATRP pore-former precursor and the UV/V absorption spectrum of anATRP liquid.

[0027]FIG. 5 provides the IR absorption spectrum for a porous OSG glassfilm deposited using a DEMS structure-former precursor and an ATRPpore-former precursor before and after UV exposure.

[0028]FIGS. 6a and 6 b provides the dielectric constant and refractiveindex versus UV exposure time for films deposited using a DEMSstructure-former precursor and an ATRP pore-former precursor undervacuum atmosphere (5 millitorr) and under nitrogen atmosphere,respectively.

[0029]FIG. 7 provides the dielectric constant and hardness (GPa) versusUV exposure time for a film deposited using a DEMS structure-formerprecursor and an ATRP pore-former precursor under vacuum atmosphere (5millitorr).

[0030]FIG. 8 illustrates the changes in the IR absorption spectrum forwavelengths ranging between 700 and 1350 cm⁻¹ for a porous OSG glassfilm deposited using a DEMS structure-former precursor and an ATRPpore-former precursor upon UV exposure under a vacuum atmosphere and fora duration ranging from 0 to 20 minutes.

[0031]FIG. 9 provides the IR absorption spectrum for a porous OSG filmdeposited using a DEMS structure-former precursor and an ATRPpore-former precursor after deposition and after exposure to UV light ina vacuum atmosphere for 1 minute and 15 minutes.

[0032]FIG. 10 provides the FT-IR absorption spectrum for a porous OSGglass film deposited using a DEMS structure-former precursor and an ATRPpore-former precursor after deposition and after exposure to UV lightand air for 5 minutes.

[0033]FIGS. 11a, 11 b, and 11 c provide the dynamic SIMS depth ofprofile measurements of silicon, oxygen, hydrogen, and carbon for aporous OSG film deposited using a DEMS structure-former precursor and anATRP pore-former precursor after deposition and after exposure to UVlight in a vacuum atmosphere for 1 minute and 15 minutes, respectively.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention is directed towards the preparation of adense or a porous organosilicate (OSG) glass material and film having alow dielectric constant but sufficient mechanical properties to make thefilm suitable for use, for example, as an interlayer dielectric inintegrated circuits. The organosilicate glass film of the presentinvention is deposited via chemical vapor deposition of at least onestructure-former precursor from the group consisting of an organosilaneor an organosiloxane. The deposited organosilicate film is then exposedto an ultraviolet (UV) radiation source to improve the mechanicalproperties, i.e., material hardness and elastic modulus (Young'smodulus) of the as-deposited film while substantially maintaining thedielectric constant of the material. In embodiments wherein theorganosilicate film is deposited via chemical vapor deposition of astructure-former and a pore-former precursor to provide a porousorganosilicate film, the mechanical properties of the porousorganosilicate film are improved after UV exposure while the dielectricconstant is reduced. Unlike other processes, the UV exposure step may,in some instances, obviate the need for a thermal annealing.

[0035] While not intending to be bound by theory, it is believed thatthe as-deposited organosilicate films formed by chemical vapordeposition contain lattice imperfections such as, for example, danglinggroups that are not incorporated into the film network. In otherorganosilicate films, these lattice imperfections may be hydrogen bondedto the silica framework as Si—H. In these films, the Si—H bonds aregenerally not broken until the material is heated to approximately 525°C., which exceeds the temperature range in which organosilicate filmscan typically be exposed to (i.e., 425° C. or below). Thus, thermaltreatments of these films to remove Si—H may not be possible. Exposureof the organosilicate film to a UV light source, particularly combinedwith the application of a heat or other energy source during at least aportion of the exposure step, removes at least a portion of thesedangling groups or the Si—H bonds and may “perfect” the film network.The composition of the as-deposited film and the post-UV exposed film issubstantially the same. However, the mechanical properties of the UVexposed film, such as the hardness and elastic modulus, is at least 10%greater, preferably 25%, and more preferably 100% greater, than themechanical properties of the as-deposited film. Further, the dielectricconstant of the UV-exposed organosilicate film is substantially the sameas, or in the case of porous organosilicate films, at least 5% lessthan, the dielectric constant of the as-deposited film. It is thussurprising and unexpected to produce low dielectric materials havingenhanced mechanical properties at relatively low temperatures.

[0036] The organosilicate glass material is preferably a film that isformed onto at least a portion of a substrate. Suitable substrates thatmay be used include, but are not limited to, semiconductor materialssuch as gallium arsenide (“GaAs”), boronitride (“BN”) silicon, andcompositions containing silicon such as crystalline silicon,polysilicon, amorphous silicon, epitaxial silicon, silicon dioxide(“SiO2”), silicon carbide (“SiC”), silicon oxycarbide (“SiOC”), siliconnitride (“SiN”), silicon carbonitride (“SiCN”), organosilicate glasses(“OSG”), organofluorosilicate glasses (“OFSG”), fluorosilicate glasses(“FSG”), and other appropriate substrates or mixtures thereof.Substrates may further comprise a variety of layers to which the film isapplied thereto such as, for example, antireflective coatings,photoresists, organic polymers, porous organic and inorganic materials,metals such as copper and aluminum, or diffusion barrier layers, e.g.,TiN, Ti(C)N, TaN, Ta(C)N, Ta, W, WN, TiSiN, TaSiN, SiCN, TiSiCN, TaSiCN,or W(C)N. The organosilicate glass films of the present invention arepreferably capable of adhering to at least one of the foregoingmaterials sufficiently to pass a conventional pull test, such as an ASTMD3359-95a tape pull test.

[0037] The organosilicate film of the present invention may be a denseor a porous film. A dense organosilicate film has a density that mayrange from about 1.5 g/cm³ to about 2.2 g/cm³. These films are typicallydeposited from at least one structure-former precursor, preferably anorganosilane or organosiloxane precursor.

[0038] In other embodiments of the present invention, the organosilicatefilm is a porous or composite film. These films are typically comprisedof at least one structure-former material and at least one pore-formermaterial and are deposited by at least one structure-former precursorand at least one pore-former precursor. The at least one pore-formermaterial may be dispersed within the structure-former material. The term“dispersed” as used herein includes discrete areas of pore-formermaterial, air-gap (i.e., relatively large areas of pore-former materialcontained within a structure-former shell), or bicontinuous areas of thestructure-former and the pore-former materials. While not intending tobe bound by theory, it is believed that the porous organosilicate film,when exposed to one or more energy sources, adsorbs a certain amount ofenergy to enable the removal of at least a portion of the pore-formermaterial from the as-deposited film while leaving the bonds within thestructure-former material intact. Depending upon the energy source andthe chemistry of the pore-former material, the chemical bonds within thepore-former material may be broken thereby facilitating its removal fromthe material. In this manner, the pore-former material may besubstantially removed from the organosilicate film thereby leaving aporous film that consists essentially of the structure-former material.The resultant porous organosilicate film, after exposure to one or moreenergy sources, may exhibit a lower density and lower dielectricconstant than the as-deposited film.

[0039] The organosilicate glass (OSG) film of the present inventioncomprises a structure-former material that is capable of forming andmaintaining an interconnecting network. Examples of the organosilicateglass films and the structure-former material contained therein include,but are not limited to, silicon carbide (SiC), hydrogenated siliconcarbide (Si:C:H), silicon oxycarbide (Si:O:C), silicon oxynitride(Si:O:N), silicon nitride (Si:N), silicon carbonitride (Si:C:N),fluorosilicate glass (Si:O:F), organofluorosilicate glass (Si:O:C:H:F),organosilicate glass (Si:O:C:H), diamond-like carbon, borosilicate glass(Si:O:B:H), or phosphorous doped borosilicate glass (Si:O:B:H:P).

[0040] In certain preferred embodiment, the structure-former materialcomprises a silica compound. The term “silica”, as used herein, is amaterial that has silicon (Si) and oxygen (O) atoms, and possiblyadditional substituents such as, but not limited to, other elements suchas C, H, B, N, P, or halide atoms; alkyl groups; or aryl groups. Incertain preferred embodiments, the structure-former material maycomprise an OSG compound represented by the formulaSi_(v)O_(w)C_(x)H_(y)F_(z), where v+w+x+y+z=100%, v is from 10 to 35atomic %, w is from 10 to 65 atomic %, x is from 5 to 30 atomic %, y isfrom 10 to 50 atomic % and z is from 0 to 15 atomic %. Regardless ofwhether or not the structure-former is unchanged throughout theinventive process, the term “structure-former” as used herein isintended to encompass structure-forming reagents or precursors (orstructure-forming substituents) and derivatives thereof, in whateverforms they are found throughout the entire process of the invention.

[0041] In embodiments wherein the organosilicate film is porous, theorganosilicate film comprises at least one pore-former material inaddition to the structure-former material. The pore-former materialcomprises a compound(s) that is capable of being easily and preferablysubstantially removed from the organosilicate film upon exposure to oneor more energy sources. The pore-former material may also be referred toas a porogen. A “pore-former”, as used herein, is a reagent that is usedto generate void volume within the resultant film. Regardless of whetheror not the pore-former is unchanged throughout the inventive process,the term “pore-former” as used herein is intended to encompasspore-forming reagents or precursors (or pore-forming substituents) andderivatives thereof, in whatever forms they are found throughout theentire process of the invention. Suitable compounds to be used aspore-former precursors include, but are not limited to, hydrocarbonmaterials, labile organic groups, decomposable polymers, surfactants,dendrimers, hyper-branched polymers, polyoxyalkylene compounds, orcombinations thereof.

[0042] As mentioned previously, the organosilicate films are depositedonto at least a portion of a substrate from a precursor composition ormixture using a variety of different methods. These methods may be usedby themselves or in combination. Some examples of processes that may beused to form the organosilicate film include the following: thermalchemical vapor deposition, plasma enhanced chemical vapor deposition(“PECVD”), high density PECVD, photon assisted CVD, plasma-photonassisted CVD, cryogenic chemical vapor deposition, chemical assistedvapor deposition, hot-filament chemical vapor deposition, photoinitiated chemical vapor deposition, CVD of a liquid polymer precursor,deposition from supercritical fluids, or transport polymerization(“TP”). U.S. Pat. Nos. 6,171,945, 6,054,206, 6,054,379, 6,159,871 and WO99/41423 provide some exemplary CVD methods that may be used to form theorganosilicate film of the present invention. In certain preferredembodiments, the deposition is conducted at a temperature ranging from100 to 425° C., preferably from 250 to 425° C. Although the chemicalreagents used herein may be sometimes described as “gaseous”, it isunderstood that the chemical reagents may be delivered directly as a gasto the reactor, delivered as a vaporized liquid, a sublimed solid and/ortransported by an inert carrier gas into the reactor.

[0043] In preferred embodiments of the present invention, theorganosilicate film is formed through a plasma-enhanced chemical vapordeposition process. Briefly in a PECVD process, chemical reagents areflowed into a reaction chamber such as a vacuum chamber and plasmaenergy energizes the chemical reagents thereby forming a film on atleast a portion of the substrate. In these embodiments, theorganosilicate film can be formed by the co-deposition, or alternativelythe sequential deposition, of a gaseous mixture comprising at least onesilica containing, preferably organosilicon material, that forms thestructure-former material with at least one plasma-polymerizable organicmaterial that forms the pore-former material. In certain embodiments,the plasma energy applied to the reagents may range from 0.02 to 7watts/cm², more preferably 0.3 to 3 watts/cm². Flow rates for each ofthe reagents may range from 10 to 5000 standard cubic centimeters perminute (sccm). Pressure values in the vacuum chamber during depositionfor a PECVD process of the present invention may range from 0.01 to 600torr, more preferably 1 to 10 torr. It is understood, however, thatprocess parameters such as plasma energy, flow rate, and pressure mayvary depending upon numerous factors such as the surface area of thesubstrate, the structure-former and pore-former precursors used, theequipment used in the PECVD process, etc.

[0044] In a certain preferred embodiment of the present inventionwherein the organosilicate glass film consists essentially of Si, C, O,H, and optionally F, the film is formed by providing a substrate withina vacuum chamber; introducing into the vacuum chamber chemical reagentsthat comprise at least one structure-former precursor selected from thegroup consisting of an organosilane and an organosiloxane, andoptionally a pore-former precursor distinct from the at least onestructure-former precursor; and applying energy to the reagents in saidchamber to induce reaction of the reagents and to form the film on thesubstrate. Examples of chemical reagents used as structure-former andpore-former precursors may be found in pending U.S. Patent ApplicationsAttorney Docket Nos. 06063USA, 06274PUSA, 06150USA, and 06336PUSA, whichare commonly assigned to the assignee of the present invention andincorporated herein by reference in its entirety.

[0045] Silica-containing compounds such as organosilanes andorganosiloxanes are the preferred precursors to form thestructure-former material of the organosilicate glass film. Suitableorganosilanes and organosiloxanes include, e.g.: (a) alkylsilanesrepresented by the formula R¹ _(n)SiR² _(4-n), where n is an integerfrom 1 to 3; R¹ and R² are independently at least one branched orstraight chain C, to C₈ alkyl group (e.g., methyl, ethyl), a C₃ to C₈substituted or unsubstituted cycloalkyl group (e.g., cyclobutyl,cyclohexyl), a C₃ to C₁₀ partially unsaturated alkyl group (e.g.,propenyl, butadienyl), a C₆ to C₁₂ substituted or unsubstituted aromatic(e.g., phenyl, tolyl), a corresponding linear, branched, cyclic,partially unsaturated alkyl, or aromatic containing alkoxy group (e.g.,methoxy, ethoxy, phenoxy), and R² is alternatively hydride (e.g.,methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane,phenylsilane, methylphenylsilane, cyclohexylsilane, tert-butylsilane,ethylsilane, diethylsilane, tetraethoxysilane, dimethyldiethoxysilane,dimethyldimethoxysilane, dimethylethoxysilane, methyltriethoxysilane,methyldiethoxysilane, triethoxysilane, trimethylphenoxysilane andphenoxysilane); (b) a linear organosiloxane represented by the formulaR¹(R² ₂SiO)_(n)SiR² ₃ where n is an integer from 1 to 10, or a cyclicorganosiloxane represented by the formula (R¹R²SiO)_(n) where n is aninteger from 2 to 10 and R¹ and R² are as defined above (e.g.,1,3,5,7-tetramethylcyclotetrasiloxane, octamethylcyclotetrasiloxane,hexamethylcyclotrisiloxane, hexamethyldisiloxane,1,1,2,2-tetramethyldisiloxane, and octamethyltrisiloxane); and (c) alinear organosilane oligomer represented by the formula R²(SiR¹R²)_(n)R²where n is an integer from 2 to 10, or cyclic organosilane representedby the formula (SiR¹R²)_(n), where n is an integer from 3 to 10, and R¹and R² are as defined above (e.g., 1,2-dimethyldisilane,1,1,2,2-tetramethyldisilane, 1,2-dimethyl-1,1,2,2-dimethoxydisilane,hexamethyldisilane, octamethyltrisilane,1,2,3,4,5,6-hexaphenylhexasilane, 1,2-dimethyl-1,2-diphenyldisilane and1,2-diphenyldisilane). In certain embodiments, theorganosilane/organosiloxane is a cyclic alkylsilane, a cyclicalkylsiloxane, a cyclic alkoxysilane or contains at least one alkoxy oralkyl bridge between a pair of Si atoms, such as 1,2-disilanoethane,1,3-disilanopropane, dimethylsilacyclobutane,1,2-bis(trimethylsiloxy)cyclobutene,1,1-dimethyl-1-sila-2,6-dioxacyclohexane,1,1-dimethyl-1-sila-2-oxacyclohexane, 1,2-bis(trimethylsiloxy)ethane,1,4-bis(dimethylsilyl)benzene, octamethyltetracyclosiloxane (OMCTS), or1,3-(dimethylsilyl)cyclobutane. In certain embodiments, theorganosilane/organosiloxane contains a reactive side group selected fromthe group consisting of an epoxide, a carboxylate, an alkyne, a diene,phenyl ethynyl, a strained cyclic group and a C₄ to C₁₀ group which cansterically hinder or strain the organosilane/organosiloxane, such astrimethylsilylacetylene, 1-(trimethylsilyl)-1,3-butadiene,trimethylsilylcyclopentadiene, trimethylsilylacetate, anddi-tert-butoxydiacetoxysilane.

[0046] In certain embodiments, the at least one structure-formermaterial further comprises fluorine. Preferred fluorine-providingchemical reagents for a PECVD-deposited organosilicate film lack any F—Cbonds (i.e., fluorine bonded to carbon), which could end up in the film.Thus, preferred fluorine-providing reagents include, e.g., SiF₄, NF₃,F₂, HF, SF₆, ClF₃, BF₃, BrF₃, SF₄, NF₂Cl, FSiH₃, F₂SiH₂, F₃SiH,organofluorosilanes and mixtures thereof, provided that theorganofluorosilanes do not include any F—C bonds. Additional preferredfluorine-providing reagents include the above mentioned alkylsilanes,alkoxysilanes, linear and cyclic organosiloxanes, linear and cyclicorganosilane oligomers, cyclic or bridged organosilanes, andorganosilanes with reactive side groups, provided a fluorine atom issubstituted for at least one of the silicon substituents, such thatthere is at least one Si—F bond. More specifically, suitablefluorine-providing reagents include, e.g., fluorotrimethylsilane,difluorodimethylsilane methyltrifluorosilane, flurotriethoxysilane,1,2-difluoro-1,1,2,2,-tetramethyldisilane, or difluorodimethoxysilane.

[0047] In certain preferred embodiments, the mixture used to form theorganosilicate film preferably comprises a silica source that may formthe structure-former material. A “silica source”, as used herein, is acompound having silicon (Si) and oxygen (O), and possibly additionalsubstituents such as, but not limited to, other elements such as H, B,C, P, or halide atoms; alkyl groups; or aryl groups. The term “alkyl” asused herein includes straight chain, branched, or cyclic alkyl groups,preferably containing from 1 to 24 carbon atoms, or more preferably from1 to 13 carbon atoms. This term applies also to alkyl moieties containedin other groups such as haloalkyl, alkaryl, or aralkyl. The term “alkyl”further applies to alkyl moieties that are substituted. The term “aryl”as used herein includes six to twelve member carbon rings havingaromatic character. The term “aryl” also applies to aryl moieties thatare substituted. The silica source may include materials that have ahigh number of Si—O bonds, but can further include Si—O—Si bridges,Si—R—Si bridges, Si—C bonds, Si—F bonds, Si—H bonds or a portion of thematerial can also have C—H bonds. Other examples of a silica source mayinclude a fluorinated silane or fluorinated siloxane such as thoseprovided in U.S. Pat. No. 6,258,407. Another example of a silica sourcemay include compounds that produce a Si—H bond upon removal of thepore-former material.

[0048] Still other examples of silica sources include silsesquioxanessuch as hydrogen silsesquioxanes (HSQ, HSiO_(1,5)) and methylsilsesquioxanes (MSQ, RSiO_(1,5) where R is a methyl group).

[0049] Further examples of the suitable silica sources include thosedescribed in U.S. Pat. No. 6,271,273 and EP Nos. 1,088,868; 1,123,753,and 1,127,929. In preferred embodiments, the silica source may be acompound represented by the following: R_(a)Si(OR¹)_(4−a), wherein Rrepresents a hydrogen atom, a fluorine atom, or a monovalent organicgroup; R¹ represents a monovalent organic group; and a is an integer of1 or 2; Si(OR²)₄, where R² represents a monovalent organic group; or R³_(b)(R⁴O)₃ Si—(R⁷)_(d)—Si(OR⁵)_(3-c)R⁶ _(c), wherein R³ to R⁶ may be thesame or different and each represents a monovalent organic group; b andc may be the same or different and each is a number of 0 to 2; R⁷represents an oxygen atom, a phenylene group, or a group represented by—(CH₂)_(n), wherein n is an integer of 1 to 6; d is 0 or 1; orcombinations thereof. The term “monovalent organic group” as used hereinrelates to an organic group bonded to an element of interest, such as Sior 0, through a single C bond, i.e., Si—C or O—C.

[0050] In embodiments wherein a porous OSG film is formed, at least oneof the gaseous reagents is a pore-former precursor. The pore-formerprecursor is preferably deposited in the same manner as thestructure-former precursor. The pore-former precursor can be deposited,for example, in a mixture with the structure-former precursor,co-deposited with the structure-former precursor, or deposited in analternating fashion with the structure-former precursor. In subsequentprocess steps, the pore-former precursor is used to generate void volumewithin the resultant porous film upon its removal. The pore-former inthe porous OSG film may or may not be in the same form as thepore-former within the mixture and/or introduced to the reactionchamber. As well, the pore-former removal process may liberate thepore-former or fragments thereof from the film. In essence, thepore-former reagent (or pore-former substituent attached to theprecursor), the pore-former in the organosilicate film, and thepore-former being removed may or may not be the same species, althoughit is preferable that they all originate from the pore-former reagent(or pore-former substituent).

[0051] In certain embodiments of the present invention, the pore-formermay be a hydrocarbon compound, preferably having from 1 to 13 carbonatoms. Examples of these compounds include, but are not limited to,alpha-terpinene, limonene, cyclohexane, gamma-terpinene, camphene,dimethylhexadiene, ethylbenzene, norbornadiene, cyclopentene oxide,1,2,4-trimethylcyclohexane, 1,5-dimethyl-1,5-cyclooctadiene, camphene,adamantane, 1,3-butadiene, substituted dienes, alpha-pinene,beta-pinene, and decahydronaphthelene.

[0052] In certain embodiments of the present invention, the pore-formermay include labile organic groups. When some labile organic groups arepresent in the reaction mixture, the labile organic groups may containsufficient oxygen to convert to gaseous products during the cure step.In yet other embodiments of the present invention, a film is depositedvia CVD from a mixture comprising the labile organic groups with aperoxide compound followed by thermal annealing. Some examples ofcompounds containing labile organic groups include the compoundsdisclosed in U.S. Pat. No. 6,171,945, which is incorporated herein byreference in its entirety.

[0053] The pore-former could also be a decomposable polymer. Thedecomposable polymer may be radiation decomposable. The term “polymer”,as used herein, also encompasses the terms oligomers and/or copolymersunless expressly stated to the contrary. Radiation decomposable polymersare polymers that decompose upon exposure to radiation, e.g.,ultraviolet, X-ray, electron beam, or the like. Examples of thesepolymers include polymers that have an architecture that provides athree-dimensional structure such as, but not limited to, blockcopolymers, i.e., diblock, triblock, and multiblock copolymers; starblock copolymers; radial diblock copolymers; graft diblock copolymers;cografted copolymers; dendrigraft copolymers; tapered block copolymers;and combinations of these architectures. Further examples of degradablepolymers are found in U.S. Pat. No. 6,204,202, which is incorporatedherein by reference in its entirety.

[0054] The pore-former may be a hyper branched or dendrimeric polymer.Hyper branched and dendrimeric polymers generally have low solution andmelt viscosities, high chemical reactivity due to surface functionality,and enhanced solubility even at higher molecular weights. Somenon-limiting examples of suitable decomposable hyper-branched polymersand dendrimers are provided in “Comprehensive Polymer Science”, 2ndSupplement, Aggarwal, pp. 71-132 (1996) which is incorporated herein byreference in its entirety.

[0055] In certain embodiments of the present invention, a singlecompound may function as both the structure-former and pore-formerwithin the porous OSG film. That is, the structure-former precursor andthe pore-former precursor are not necessarily different compounds, andin certain embodiments, the pore-former is a part of (e.g., covalentlybound to) the structure-former precursor. Examples of these materialsmay be found, for example, in pending U.S. Patent Applications, AttorneyDocket Nos. 06150USA and 06274PUSA, that are commonly assigned to theassignee of the present invention and incorporated herein by referencein its entirety. For example, it is possible to use1-neohexyl-1,3,5,7-tetramethyl-cyclotetrasiloxane (“neohexyl TMCTS”) asa single species, whereby the TMCTS portion of the molecule forms thebase OSG structure and the bulky alkyl substituent neohexyl is thepore-former species which is removed, for example, during the annealprocess. Having the pore-former attached to a Si species that willnetwork into the OSG structure may be advantageous in achieving a higherefficiency of incorporation of pore-former into the film during thedeposition process. Furthermore, it may also be advantageous to have twopore-formers attached to one Si in the precursor, such as indi-neohexyl-diethoxysilane, or two Si's attached to one pore-former,such as in 1,4-bis(diethoxysilyl)cyclohexane. While not intending to bebound by theory, the reaction of one Si-pore-former bond in the plasmamay enable the the incorporation of the second pore-former group intothe deposited film.

[0056] In certain embodiments of the materials in which a single ormultiple pore-former is attached to silicon, it may be advantageous todesign the pore-former in such a way that when the film is cured to formthe pores, a part of the pore-former remains attached to the silicon toimpart hydrophobicity to the film. Under proper conditions this it isbelieved that this would leave a terminal —CH₃ group bonded to the Si toprovide hydrophobicity and a relatively lower dielectric constant to thefilm. Examples of precursors are neopentyl triethoxysilane, neopentyldiethoxy silane, and neopentyl diethoxymethylsilane.

[0057] In certain embodiments of the present invention, an additionalreagent such as a reducing agent may be added to the environment duringthe pore-former removal process. The additional reagent may be added toenhance the removal of the one or more pore-former materials from theorganosilicate film.

[0058]FIGS. 1a through 1 c provide an illustration of one embodiment ofthe method of the present invention for forming a porous OSG film.Referring to FIG. 1a, a film 100 is formed upon at least a portion of asubstrate 50. Film 100 comprises at least two materials: at least onestructure-former material 110 and at least one pore-former material 120dispersed within the structure-former material 110. In certain preferredembodiments, the structure-former material 110 is a compound containingprimarily Si:O:C:H and the at least one pore-former material 120 is anorganic compound containing primarily C:H. In FIG. 1b, film 100 isexposed to one or more energy sources such as ultraviolet light 130. Theexposure step depicted in FIG. 1b may be conducted at one or moretemperatures below 425° C. and for a short time interval therebyconsuming as little of the overall thermal budget of substrate 50 aspossible. Referring now to FIG. 1c, the pore-former material 120 issubstantially removed from film 100 leaving a porous OSG film 140. Theresultant porous film 140 will have a lower dielectric constant, atleast 5% or less than, and a higher material hardness and modulus, atleast 10%, preferably at least 25% or greater than the dielectricconstant, material hardness and modulus of the as-deposited film 100prior to exposure.

[0059] As mentioned previously, the dense or porous OSG film is exposedto one or more ultraviolet light sources ranging from 200 to 400 nm toenhance the mechanical properties of the film. This exposure step can bein lieu of, or in addition to, an annealing step. The temperature thatthe substrate is subjected to during exposure to an ultraviolet lightsource typically ranges from between 25 to 425° C. The dielectricconstant of the structure-former material(s) remains essentially thesame by the exposure to the ultraviolet light source.

[0060] The organosilicate film may be exposed to one or more wavelengthswithin the ultraviolet spectrum or one or more wavelengths within theultraviolet spectrum such as deep ultraviolet light (i.e., wavelengthsof 280 nm or below) or vacuum ultraviolet light (i.e., wavelengths of200 nm or below). The ultraviolet light may be dispersive, focused,continuous wave, pulsed, or shuttered. Sources for the ultraviolet lightinclude, but are not limited to, an excimer laser, a barrier dischargelamp, a mercury lamp, a microwave-generated UV lamp, a laser such as afrequency doubled or frequency tripled laser in the IR or visibleregion, or a two-photon absorption from a laser in the visible region.The ultraviolet light source may be placed at a distance that rangesfrom 50 milli-inches to 1,000 feet from the organosilicate film.

[0061] In certain preferred embodiments, the exposure step is conductedin a non-oxidizing atmosphere such as an inert atmosphere (e.g.,nitrogen, helium, argon, xenon, krypton, radon, etc.), a reducingatmosphere (e.g., H₂, CO), or vacuum. It is believed that the presenceof oxygen during the exposure step may substantially modify thestructure forming material(s) of the film and/or increase the dielectricconstant of the film. Further, it is believed that the presence ofoxygen may interfere with the removal of the pore-former precursor inembodiments where a porous OSG film is formed.

[0062] The organosilicate film may be exposed to one or more specificwavelength within the UV light source or a broad spectrum ofwavelengths. For example, the composite film may be exposed to one ormore particular wavelengths of light such as through a laser and/oroptically focused light source. In the latter embodiments, the radiationsource may be passed through optics such as lenses (e.g., convex,concave, cylindrical, elliptical, square or parabolic lenses), filters(e.g., RF filter), windows (e.g., glass, plastic, fused silica,synthetic silica, silicate, calcium fluoride, lithium fluoride, ormagnesium fluoride windows) or mirrors to provide specific and focusedwavelengths of light. In these embodiments, a non-reactive gas may beflowed over the optics during at least a portion of the exposing step toprevent the formation of build-up on the surface of the optics formed byoff-gassing during the pore-formation step. Alternatively, the radiationsource does not pass through any optics.

[0063] In certain embodiments, the ultraviolet light source is passedthrough optics to keep the temperature of the substrate relatively lowduring the exposing step by adjusting the ultraviolet light to aparticular wavelength. For example, FIG. 4 provides the UV/visible lightabsorption spectrum of an as-deposited film deposited from a DEMSstructure-former precursor and an ATRP pore-former precursor and theUV/visible light absorption spectrum of an ATRP liquid. The spectrumshows a peak at a wavelength of 265 nm, which relates to the presence ofC—C bonds within the film. Providing a focused UV light source in the265 nm wavelength range may remove the ATRP pore-former in less time andat a lower substrate temperature. Specific temperature and timedurations for the exposure step may vary depending upon the chemicalspecies used to form the organosilicate film. In certain preferredembodiments, the exposure step is conducted at a temperature below about425° C., preferably below about 300° C., and more preferably below about250° C. The exposure step is conducted for a time of about 60 minutes orless, preferably about 10 minutes or less, and more preferably about 10seconds or less. In certain embodiments of the present invention, thetemperature of the substrate having the OSG film deposited thereuponranges from 25 to 425° C., preferably 250 to 425° C. In theseembodiments, the substrate may be placed on a heated platform, platen,or the like.

[0064] The exposure step may be conducted in a variety of settingsdepending upon the process used to form the organosilicate film. It maybe advantageous for the exposure step to be conducted after or evenduring at least a portion of the organosilicate film formation step. Theexposure step can be performed in various settings such as, but notlimited to, quartz vessel, a modified deposition chamber, a conveyorbelt process system, a hot plate, a vacuum chamber, a cluster tool, asingle wafer instrument, a batch processing instrument, or a rotatingturnstile.

[0065] The organosilicate film of the present invention may be furthersubjected to other post deposition steps such as treating the porousfilm with one or more energy sources. The energy source for the treatingstep may include, but not be limited to, α-particles, β-particles,γ-rays, x-rays, high energy electron, electron beam sources of energy,ultraviolet (wavelengths ranging from 10 to 400 nm), visible(wavelengths ranging from 400 to 750 nm), infrared (wavelengths rangingfrom 750 to 10⁵ nm), microwave frequency (>10⁹ Hz), radio-frequency(>10⁶ Hz), thermal sources; plasma; or mixtures thereof. This treatmentstep may be performed before, during, or after the exposing step.Preferably, the treatment step may be performed prior to, or during, atleast a portion of the exposing step. The treatment step may furtherincrease the mechanical integrity of the material by, for example,promoting cross-linking within the porous film, stabilize the porousfilm, and/or remove additional chemical species from the network duringat least a portion of the removal of the pore-former precursor.

[0066] The one or more energy sources can include any of the energysources disclosed herein as well as thermal sources such as a hot plate,oven, furnace, RTA (rapid thermal annealing), infrared radiationsources, and the like. In certain preferred embodiments, the treatmentstep is conducted using thermal energy prior to and/or during at least aportion of the UV exposure step. In these embodiments, the mechanicalproperties of the film may be substantially increased in comparison tothermal annealing and/or UV exposure alone.

[0067] In another embodiment of the present invention, the treatmentstep may be conducted using UV light. This treatment step differs fromthe UV exposure step in that the exposure step substantially removes thepore-former material from the organosilicate film to provide a porousfilm and the treatment step may, for example, improve the mechanicalproperties of the film such as hardness and modulus. For example, the UVexposure step may occur for a duration ranging from about 0.1 to about 5minutes, preferably about 0.1 to about 1 minute, to substantially removethe pore-former material contained therein and provide the porous OSGfilm; the UV treatment step may occur thereafter for a duration rangingfrom about 1 to about 20 minutes, preferably about 5 to about 20minutes. Both UV exposure and UV treatment steps may be conducted usingthe same lamp, purge gas chemistry, and/or chamber to improve processthroughput. In these embodiments, further post-treatment steps, such astreatment with other energy sources and/or chemical treatments, may alsobe conducted.

[0068] The conditions under which the treatment step is conducted canvary greatly. For example, the treatment step can be conducted underhigh pressure or under a vacuum ambient. The environment can be inert(e.g., nitrogen, CO₂, noble gases (He, Ar, Ne, Kr, Xe), etc.), oxidizing(e.g., oxygen, air, dilute oxygen environments, enriched oxygenenvironments, ozone, nitrous oxide, etc.) or reducing (dilute orconcentrated hydrogen, hydrocarbons (saturated, unsaturated, linear orbranched, aromatics), etc.). The pressure is preferably about 1 Torr toabout 1000 Torr, more preferably atmospheric pressure. However, a vacuumambient is also possible for thermal energy sources as well as any otherpost-treating means. The temperature may range from 25 to 450° C.,preferably from 200 to 450° C. The temperature ramp rate may range from0.1 to 100 deg ° C./min. The total treatment time may range from 0.01min to 12 hours, preferably from 1 to 240 min.

[0069] In certain embodiments of the present invention, the OSG film maybe subjected to a chemical treatment that may include, for example, theuse of fluorinating (HF, SiF₄, NF₃, F₂, COF₂, CO₂F₂, etc.), oxidizing(H₂O₂, 03, etc.), chemical drying, methylating, or other chemicaltreatments. Chemicals used in such treatments can be in solid, liquid,gaseous and/or supercritical fluid states. In certain embodiments,supercritical fluid treatment may be used to treat the film. The fluidcan be carbon dioxide, water, nitrous oxide, ethylene, SF₆, and/or othertypes of chemicals. Other chemicals can be added to the supercriticalfluid to enhance the process. The chemicals can be inert (e.g.,nitrogen, CO₂, noble gases (He, Ar, Ne, Kr, Xe), etc.), oxidizing (e.g.,oxygen, ozone, nitrous oxide, etc.), or reducing (e.g., dilute orconcentrated hydrocarbons, hydrogen, etc.). The temperature ispreferably ambient to 500° C. The chemicals can also include largerchemical species such as surfactants. The total exposure time ispreferably from 0.01 min to 12 hours.

[0070] In embodiments wherein the OSG film is treated with a plasma, theplasma is conducted under the following conditions: the environment canbe inert (nitrogen, CO₂, noble gases (He, Ar, Ne, Kr, Xe), etc.),oxidizing (e.g., oxygen, air, dilute oxygen environments, enrichedoxygen environments, ozone, nitrous oxide, etc.), or reducing (e.g.,dilute or concentrated hydrogen, hydrocarbons (saturated, unsaturated,linear or branched, aromatics), etc.). The plasma power is preferably0-10 W/cm³. The temperature preferably ranges from ambient to 425° C.The pressure preferably ranges from 10 mtorr to atmospheric pressure.The total treatment time is preferably 0.01 min to 12 hours.

[0071] Photocuring post-treatment may be conducted under the followingconditions: the environment can be inert (e.g., nitrogen, CO₂, noblegases (He, Ar, Ne, Kr, Xe), etc.), or reducing (e.g., dilute orconcentrated hydrocarbons, hydrogen, etc.). The temperature ispreferably ambient to 425° C. The power is preferably 0-10 W/cm³. Thewavelength is preferably IR, visible, UV or deep UV (wavelengths <200nm). The total curing time is preferably 0.01 min to 12 hours.

[0072] Microwave post-treatment may be conducted under the followingconditions: the environment can be inert (e.g., nitrogen, CO₂, noblegases (He, Ar, Ne, Kr, Xe), etc.), oxidizing (e.g., oxygen, air, diluteoxygen environments, enriched oxygen environments, ozone, nitrous oxide,etc.), or reducing (e.g., dilute or concentrated hydrocarbons, hydrogen,etc.). The temperature is preferably ambient to 500° C. The power andwavelengths are varied and tunable to specific bonds. The total curingtime is preferably from 0.01 min to 12 hours.

[0073] Electron beam post-treatment may be conducted under the followingconditions: the environment can be vacuum, inert (e.g., nitrogen, CO₂,noble gases (He, Ar, Ne, Kr, Xe), etc.), oxidizing (e.g., oxygen, air,dilute oxygen environments, enriched oxygen environments, ozone, nitrousoxide, etc.), or reducing (e.g., dilute or concentrated hydrocarbons,hydrogen, etc.). The temperature is preferably ambient to 500° C. Theelectron density and energy can be varied and tunable to specific bonds.The total curing time is preferably from 0.001 min to 12 hours, and maybe continuous or pulsed. Additional guidance regarding the general useof electron beams is available in publications such as: S. Chattopadhyayet al., Journal of Materials Science, 36 (2001) 4323-4330; G. Kloster etal., Proceedings of IITC, Jun. 3-5, 2002, SF, CA; and U.S. Pat. Nos.6,207,555 B1, 6,204,201 B1 and 6,132,814 A1.

[0074] In certain embodiments of the present invention, theorganosilicate films are porous. The average pore sizes within theporous film ranges from about 1 Å to about 500 Å, preferably from about1 Å to about 100 Å, and most preferably from about 1 Å to about 50 Å. Itis preferred that the film have pores of a narrow size range and thatthe pores are homogeneously distributed throughout the film. However,the porosity of the film need not be homogeneous throughout the film. Incertain embodiments, there is a porosity gradient and/or layers ofvarying porosities. Such films can be provided by, e.g., adjusting theratio of pore-former material to structure-former material duringformation of the porous organosilicate film. The porosity of the filmsmay have continuous or discontinuous pores. The porous films of theinvention preferably have a density of 2.0 g/cm³ or less, oralternatively, 1.5 g/cm³ or less, or 1.25 g/cm³ or less. Preferably, theporous films of the invention have a density at least 10% less,preferably at least 25% less, and more preferably at least 50% less thanthe density of the unexposed film.

[0075] The porous films of the invention have a lower dielectricconstant relative to the dense OSG materials. Dense OSG films has adielectric constant ranging from 2.7 to 3.5 whereas porous OSG films ofthe invention have a dielectric constant of about 2.7 or below,preferably about 2.4 or below, and more preferably about 2.2 or below.

[0076] In certain embodiments, the dense or porous OSG films of theinvention are thermally stable, with good chemical resistance. Inparticular, the films after the UV exposure step have an average weightloss of less than 1.0 wt %/hr isothermal at 425° C. under N2.

[0077] The films are suitable for a variety of uses. The films areparticularly suitable for deposition on a semiconductor substrate, andare particularly suitable for use as, e.g., an insulation layer, aninterlayer dielectric layer and/or an intermetal dielectric layer. Thefilms can form a conformal coating. The properties exhibited by thesefilms make them particularly suitable for use in Al subtractivetechnology and Cu damascene or dual damascene technology.

[0078] Because of their enhanced mechanical properties, the films arecompatible with chemical mechanical planarization (CMP) and anisotropicetching, and are capable of adhering to a variety of substratematerials, such as silicon, SiO₂, Si₃N₄, OSG, FSG, silicon carbide,hydrogenated silicon carbide, silicon nitride, hydrogenated siliconnitride, silicon carbonitride, hydrogenated silicon carbonitride,boronitride, antireflective coatings, photoresists, organic polymers,porous organic and inorganic materials, metals such as copper andaluminum, and diffusion barrier layers such as but not limited to TiN,Ti(C)N, TaN, Ta(C)N, Ta, W, or WN.

[0079] The present invention also discloses a mixture for forming adense or a porous OSG film having a dielectric constant of 3.5 or belowsuitable for exposure to UV light. The OSG film may be formed by avariety of deposition processes including CVD-related and spin-on-glassprocesses. For dense OSG films, the mixture comprises at least onestructure-former precursor and/or resultant OSG film that exhibits anabsorbance in the 200 to 400 nm wavelength range. For porous OSG films,the mixture may comprise from 5% to 95% by weight of a structure-formerprecursor and from 5% to 95% by weight of a pore-former precursorwherein the at least one of the precursors and/or the organosilicatefilm exhibits an absorbance in the 200 to 400 nm wavelength range.Depending upon the deposition process, such as for spin-on-glassdeposition, the mixture may comprise additional additives, for example,a solvent, a catalyst, a surfactant, water, and the like. Additionaladditives to the mixture used for spin-on-glass deposition may be found,for example, in pending U.S. Patent Applications Attorney Docket No.06336PUSA, which is commonly assigned to the assignee of the presentinvention and incorporated herein by reference in its entirety.

[0080] The dielectric material and film of the present invention exhibita substantial uniformity in composition. Compositional uniformitydescribes a film property wherein the composition is relatively uniformwith relatively little deviation in composition from the surface to thebase of the film. A film that exhibits substantial uniformity incomposition may avoid problems associated with the formation of a “skinlayer”. For example, the use of UV light or electron beams during theexposing and/or treating steps may form a “skin layer” that iscompositionally different than the underlying bulk film because theradiation sufficient to remove the pore-former material within thecomposite film may also modify the structure-former material at thesurface where the radiation flux is maximum.

[0081] To enable comparisons, the result can be expressed as percentnon-uniformity. Preferably, the percent non-uniformity is about 10% orless, more preferably about 5% or less, most preferably about 2% orless. Compositional uniformity can be determined, for example, by usingelectrical measurements (e.g., 4-point probe), SIMS (Secondary Ion MassSpectrometry), RBS (Rutherford Backscattering Spectroscopy),Spectroscopic Ellipsometry and/or high resolution X-ray diffractometry(HR-XRD).

[0082] Compositional uniformity is preferably measured using SIMS acrossa wafer substrate onto which the OSG film has been deposited. In onepreferred method, SIMS measurements are made through the depth of thefilm. For each element in question, the distribution of that elementthrough the film is then determined from the SIMS data, and theresulting value expressed in intensity measured at a detector, which isrelated to its concentration in the film at any given depth. The valuesare then averaged, and the standard deviation determined.

[0083] For a given OSG film, compositional non-uniformity may becompared using the standard deviation divided by the sum of the maximumand minimum measured values, and the result expressed as a percentage.For example, if a dynamic SIMS depth of profile is performed at a singlepoint for a given OSG film and the average intensity of the carbonsignal is 1.255×10⁶ counts with a standard deviation of 1.987×10⁴counts, and the minimum intensity throughout the film is 1.21×10⁶ countsand the maximum intensity is 1.3×10⁶ counts, then the compositionalnon-uniformity is 0.8% because the sum of the minimum and maximum valuesis 1.51×10⁶, the standard deviation is 1.987×10⁴, and 1.987×10⁴ dividedby 1.51×10⁶ equals 0.8%.

[0084] Preferred values of compositional non-uniformity may varydepending on the amount of the element in the OSG film. If the amount ofelement is 1 atomic % or greater, the compositional non-uniformity forthe Si-containing film is about 15% or less, more preferably about 10%or less, even more preferably about 5% or less, most preferably about 1%or less. Therefore, the compositional non-uniformity of the majorelements within the OSG film, i.e., silicon, oxygen, hydrogen, andcarbon, is 15% or less, more preferably 10% or less, and most preferably5% or less.

[0085] Although the invention is particularly suitable for providingfilms and products of the invention are largely described herein asfilms, the invention is not limited thereto. Products of the inventioncan be provided in any form such as coatings, multilaminar assemblies,and other types of objects that are not necessarily planar or thin, anda multitude of objects not necessarily used in integrated circuits.Preferably, the substrate is a semiconductor.

[0086] The invention will be illustrated in more detail with referenceto the following examples, but it should be understood that the presentinvention is not deemed to be limited thereto.

EXAMPLES

[0087] Exemplary dense and porous OSG glass films were formed via aplasma enhanced CVD process using an Applied Materials Precision-5000system in a 200 mm DxZ vacuum chamber that was fitted with an AdvancedEnergy 200 rf generator from a variety of different chemical precursorsand process conditions. Unless otherwise stated, the glass films weredeposited onto low resistivity (R<0.02 Ω·cm) silicon wafers. The CVDprocess generally involved the following basic steps: initial set-up andstabilization of gas flows, deposition, and purge/evacuation of chamberprior to wafer removal. The thickness and refractive index of each filmwere measured by reflectrometry using standard methods. The dielectricconstant of each film was determined using the mercury probe capacitancetechnique on low resistivity p-type wafers (R<0.02 ohm-cm). Mechanicalproperties were determined using a MTS Nano Indenter. Transmission FTIRspectra were determined using a Thermo-Nicolet 750 Spectrophotometer at4 cm⁻¹ resolution on high resistivity wafers (R>5 ohm-cm).

[0088] Thermal post-treatment or annealing was performed in an AppliedTest Systems, Inc. series 3210 tube furnace fitted with 4″ diameterpurged quartz tube with a nitrogen purge ranging from 2 to 4 slpm. Theramp rate was 13° C. per minute from 25 to 425° C. At 425° C., the filmswere soaked for 240 minutes. The films were allowed to cool to below100° C. before removal from the furnace.

[0089] Unless otherwise stated, UV exposure was performed using a FusionUV model F305 ultraviolet lamp with an 1300 MB irradiator unit, P300power supply, and a “D” bulb, which provides radiation ranging from 200to 450 nm. The distance between the face of the irradiator unit and thesample is approximately 3 inches. The samples were contained within a 2″diameter quartz process tube equipped with either the vacuum or thenitrogen purge. The films subjected to UV exposure were placed in a 2″diameter quartz glass tube with end caps capable of sealing to nitrogenpurge or vacuum. In examples involving a vacuum or inert atmospheres,three pump and purge cycles were performed prior to UV exposure toensure that any oxygen concentrations within the sample tube were below50 ppm. Films were exposed to UV radiation for between 0 and 30 minutes.

Example 1 Formation of a Dense OSG Film Using Diethoxymethylsilane(DEMS) and Triethoxysilane (TES)

[0090] An organosilicate glass film was formed onto a silicon wafer viaplasma enhanced chemical vapor deposition (PECVD) of thestructure-former precursors DEMS (773 mg/min) and TES (773 mg/min) usingCO₂ as the carrier gas at a flow rate of 500 sccm. The deposition wasperformed at 6 torr, 600 W plasma power, and 400 milli-inch (mils)spacing between the top electrode and silicon wafer substrate. The wafertemperature during deposition was maintained at 300° C. The depositionrate of the film was 540 nm/min.

[0091] The properties of the OSG film after deposition (example 1a),after thermal anneal (example 1b), and after exposure to a UV lightsource (example 1 c) are provided in Table I. As Table I illustrates,films 1 b and 1 c, which were thermally annealed and exposed to UV lightrespectively, exhibited a slight decrease in dielectric constantrelative to example 1a or the as-deposited film. However, film 1 c alsoexhibited a significant increase in hardness, or an approximately 23%increase in hardness, from example 1a. Example 1b, by contrast,exhibited an approximately 3% increase in hardness from example 1a.Thus, the UV exposure step provides a significant improvement in themechanical properties of the OSG glass film relative to thermalpost-treatment while using milder processing conditions.

Example 2 Formation of a Dense OSG Films Using1,3-dimethyl-1,3-diethoxy-disiloxane (MEDS)

[0092] An organosilicate glass film was formed onto silicon wafer viaPECVD of 700 mg/min of the structure-former precursor MEDS and CO₂ asthe carrier gas at a flow rate of 250 sccm. The deposition was performedat 6 torr, 600 W plasma power, and 350 mils spacing. The wafertemperature during deposition was maintained at 250° C. The depositionrate of the film was 1330 nm/minute.

[0093] The properties (i.e., thickness, refractive index, dielectricconstant, and hardness) of the OSG film after deposition (example 2a),after thermal anneal (example 2b), and after exposure to a UV lightsource (example 2c) are provided in Table I. As Table I illustrates,both films 2 b and 2 c, which were thermally annealed and exposed to UVlight respectively, exhibited a slight increase in dielectric constantrelative to film 2 a or the as-deposited film. However, example film 2 cexhibited a significant increase, or approximately 96% increase, inhardness from example 2a. Example 2b, by contrast, exhibited anapproximately 14% increase in hardness from example 2a. Thus, UVexposure provides a significant improvement in the mechanical propertiesof the OSG glass film relative to thermal post-treatment using milderprocessing conditions.

Example 3 Formation of a Dense OSG Films Using Trimethylsilane (3MS)

[0094] An organosilicate glass film was formed onto silicon wafer viaPECVD of 540 sccm of the structure-former precursor 3MS and a flow rateof oxygen of 90 sccm. The deposition was performed at 4 torr, 600 Wplasma power, and 260 mils spacing. The wafer temperature duringdeposition was maintained at 350° C. The deposition rate of the film was815 nm/minute.

[0095] The properties (i.e., thickness, refractive index, dielectricconstant, and hardness) of the OSG film after deposition (example 3a)and after exposure to a UV light source (example 3b) are provided inTable I. As Table I illustrates, the exposure of film 3 b to UV lightlowered its dielectric constant by 0.09 or 4% and increased its hardnessby 0.59 GPa or 47% relative to example 3a or the as-deposited film.Thus, UV exposure provides a significant improvement in the mechanicalproperties and of the OSG glass film relative to thermal post-treatmentusing milder processing conditions and with no negative effect on itsdielectric constant. TABLE I Film Properties for Various Dense OSGmaterials Thickness Refractive Dielectric Hardness Example PrecursorLoss (5%) Index Constant (GPa) 1a DEMS/TES As N/A 1.425 3.06 1.85Deposited 1b DEMS/TES Thermal 0 1.415 3.03 1.91 1c DEMS/TES UV −3 1.4202.97 2.27 2a MEDS As N/A 1.415 2.79 0.70 Deposited 2b MEDS Thermal 01.371 2.84 0.80 2c MEDS UV −10 1.396 2.85 1.37 3a 3MS As N/A 1.445 3.071.25 Deposited 3b 3MS UV 0 1.439 2.98 1.84

Example 4 Formation of a Dense OSG Film Using Dimethyldimethoxysilane(DMDMOS)

[0096] An organosilicate glass film was formed onto a silicon wafer viaPECVD of 1250 mg/min of the structure-former precursor DMDMOS with 200sccm of a helium carrier gas and 15 sccm of O₂ as an additive. Thedeposition was performed at 12 torr, 300 W plasma power, and 300 milsspacing. The wafer temperature during deposition was maintained at 350°C. The deposition rate of the film was 110 nm/minute.

[0097] The properties of the OSG film after deposition (example 4a) andafter exposure to a UV light source (example 4b) are provided in TableII. As Table II illustrates, the UV post-treatment lowered thedielectric constant of the film by 0.1 or 6%. Further, the UVpost-treatment improved the modulus and hardness of the film by 5.7 GPAand 0.94 GPa, respectively, or approximately 270% and 274%,respectively.

Example 5 Formation of a Dense OSG Film Using Dimethyldimethoxysilane(DMDMOS)

[0098] An organosilicate glass film was formed onto a silicon wafer viaPECVD of 750 mg/min of the structure-former precursor DMDMOS with 200sccm of a helium carrier gas. The deposition was performed at 12 torr,500 W plasma power, and 300 mils spacing. The wafer temperature duringdeposition was maintained at 350° C. The deposition rate of the film was135 nm/minute

[0099] The properties of the OSG film after deposition (example 5a) andafter exposure to a UV light source (example 5b) are provided in TableII. As Table II illustrates, both the dielectric constant and hardnessof the film increased upon exposure to UV light. The UV post-treatmentincreased the dielectric constant by 0.32 or 15% and improved themodulus and hardness of the film by approximately 207% and 170%,respectively. It is not unexpected that such dramatic improvements inthe film hardness are accompanied by increases in the dielectricconstant of the film. While the lack of change in the refractive indexof the film suggests that the material density is not changedappreciably by UV exposure, it is believed that additional bonds such asSi—C—Si bonds that contribute positively to the film hardness may alsohave a negative impact on the dielectric constant. TABLE II Comparisonof Properties of Dense DMDMOS OSG Films Before and After UV ExposureThickness Refractive Dielectric Modulus Hardness Example Precursor LossIndex Constant (GPa) (GPa) 4a DMDMOS As N/A 1.387 2.75 3.36 0.54Deposited 4b DMDMOS UV  −11% 1.351 2.65 9.06 1.48 5a DMDMOS As N/A 1.4523.07 14.77 2.50 Deposited 5b DMDMOS UV   −8% 1.451 3.39 30.62 4.25

Example 6 Effect of Deposition Temperature on Dense DEMS OSG Films

[0100] Exemplary OSG films were formed onto silicon wafers via PECVDusing 1,500 mg/min of the structure-former DEMS, 150 sccm of helium asthe carrier gas, and 250 sccm CO₂ as an additive. The deposition wasperformed at 6 torr, 500 W plasma power, and 300 mils spacing. The wafertemperature during deposition was varied from 150 to 425° C. A portionof the as-deposited films was thermally annealed at 375° C., 400° C.,and 425° C. for 4 hours under a nitrogen atmosphere. Other as-depositedfilms were exposed to UV light for 15 minutes in a vacuum atmosphere.Still other as-deposited films were thermally annealed at either 375° C.or 400° C. for 4 hours each under a nitrogen atmosphere and then exposedto UV light for 15 minutes in a vacuum atmosphere.

[0101] The properties of the resultant films are provided in Table III.The relationship between hardness and dielectric constant for theas-deposited, thermal treated, and UV exposed DEMS OSG films at eachdeposition temperature is provided in FIG. 2.

[0102] Referring to Table III and FIG. 2, the deposition temperature hasa significant effect on the resultant properties of the film. There is adirect relationship between the substrate temperature at which filmdeposition occurs and the dielectric constant and hardness of the film.The deposition temperature also influences the magnitude of the changesin film properties that can be affected by post treatment steps such asthermal annealing and UV exposure. For example, DEMS OSG films depositedat temperatures <300° C. can exhibit substantial changes in dielectricconstant, refractive index, and hardness upon thermal annealing. Thismay be due to residual alkoxy groups within the as-deposited films thatare not removed during the deposition process. Both thermal anneal andUV exposure post-treatments lower the dielectric constant for DEMS OSGfilms deposited <300° C. The dielectric constants of the films depositedat temperatures <300° C. are generally decreased to a greater extent byUV exposure versus thermal annealing. However, the thermal annealpost-treatment is slightly more effective than UV treatment forimproving the modulus and hardness for films deposited <300° C.

[0103] Films deposited at temperatures >300° C. exhibit only smallchanges in either their dielectric constant or hardness after thermalannealing. This may be because thermally labile species such as alkoxygroups within the DEMS precursor chemical are removed during thedeposition process when the substrate temperature is >300° C.Consequently, there is little change in either the refractive index,dielectric constant, or hardness for these films upon thermalpost-treatment. However, UV exposure is still effective at increasingthe mechanical strength of these films while maintaining or decreasingthe dielectric constant. FIG. 2 illustrates that there is a substantialimprovement in modulus and hardness upon UV exposure for films depositedabove 300° C. In this regard, films deposited at temperatures below 300°C. did not show a regular relationship between dielectric constant andhardness whereas films deposited above 300° C. displayed a linearrelationship between dielectric constant and hardness.

[0104] The most dramatic results were observed on OSG films wherein UVexposure is preceded by a thermal anneal at 400° C. In these films, theincrease in hardness is more substantial with only a slight increase inthe dielectric constant. Reducing the temperature of thermal annealtemperature to 375° C., lessens the increase in hardness but maintainsor decreases the dielectric constant. It is believed that this may beattributable to the major loss of alkoxy groups at a temperature rangingfrom 375° C. to 400° C. The removal of the alkoxy groups may allow thefilms to be more receptive towards hardness enhancement by exposure toUV radiation. TABLE III Comparison of Deposition Temperature on DenseDEMS OSG Films Deposition Thickness Refractive Dielectric ModulusHardness Temp. Loss Index Constant (GPa) (GPa) 150° C. As Deposited N/A1.433 3.06 3.07 0.48 150° C. Thermal (375° C.) −1% 1.395 N/A N/A N/A150° C. Thermal (400° C.) −1% 1.403 N/A N/A N/A 150° C. Thermal (425°C.) −4% 1.384 2.79 5.34 0.94 150° C. Thermal (375° C.) + −16%  1.3982.82 12.18 1.93 UV 150° C. Thermal (400° C.) + −16%  1.400 2.77 11.972.03 UV 150° C. UV −6% 1.397 2.69 4.49 0.72 200° C. As Deposited N/A1.432 2.96 4.99 0.86 200° C. Thermal (375°) −1% 1.395 N/A N/A N/A 200°C. Thermal (400°) −1% 1.403 N/A N/A N/A 200° C. Thermal (425°) −2% 1.4022.81 5.33 0.92 200° C. Thermal (375° C.) + −5% 1.402 2.79 7.48 1.19 UV200° C. Thermal (400° C.) + −15%  1.411 2.87 15.10 2.49 UV 200° C. UV−1% 1.417 2.83 4.78 0.80 250° C. As Deposited N/A 1.411 3.00 5.55 0.84250° C. Thermal (375°) −1% 1.414 N/A N/A N/A 250° C. Thermal (400°) −1%1.423 N/A N/A N/A 250° C. Thermal (425° C.) −1% 1.408 2.90 7.42 1.30250° C. Thermal (375° C.) + −5% 1.395 2.92 8.19 1.33 UV 250° C. Thermal(400° C.) + −15%  1.433 3.03 22.66 3.2 UV 250° C. UV −1% 1.413 2.85 7.511.29 300° C. As Deposited N/A 1.433 3.00 10.30 1.80 300° C. Thermal(375°) −1% 1.420 N/A N/A N/A 300° C. Thermal (400°) −1% 1.427 N/A N/AN/A 300° C. Thermal −1% 1.430 3.01 10.90 1.94 300° C. Thermal (375°C.) + −2% 1.420 2.99 11.68 1.90 UV 300° C. Thermal (400° C.) + −12% 1.419 3.21 25.48 3.56 UV 300° C. UV −1% 1.407 2.99 12.58 2.15 350° C. AsDeposited N/A 1.440 3.12 15.43 2.65 350° C. Thermal (375°)   0% 1.440N/A N/A N/A 350° C. Thermal (400°)   0% 1.433 N/A N/A N/A 350° C.Thermal   0% 1.442 3.09 15.93 2.68 350° C. Thermal (375° C.) + −2% 1.4423.05 18.33 2.87 UV 350° C. Thermal (400° C.) + −8% 1.462 3.28 28.96 4.00UV 350° C. UV −2% 1.446 3.05 17.78 2.94 425° C. As Deposited N/A 1.4793.34 26.05 4.17 425° C. Thermal (375° C.)   0% 1.461 N/A N/A N/A 425° C.Thermal (400° C.)   0% 1.475 N/A N/A N/A 425° C. Thermal   0% 1.479 3.3226.61 4.18 425° C. Thermal (375° C.) + −2% 1.472 3.30 31.73 4.54 UV 425°C. Thermal (400° C.) + −3.5%   1.473 3.42 33.50 4.76 UV 425° C. UV −2%1.474 3.27 30.09 4.59

Examples 7 and 8 Formation of a Dense OSG Film Using1,3,5,7-Tetramethylcyclotetrasiloxane (TMCTS) at various substratetemperatures

[0105] Organosilicate glass films were formed onto a silicon wafers viaPECVD of 750 mg/min of the structure-former precursor TMCTS with 500sccm of a helium carrier gas. The depositions were performed at 6 torr,300 W plasma power, and 320 mils spacing. The wafer temperature duringdeposition was maintained at 350° C. or 425° C. The deposition rate ofthe film was 990 nm/minute at 350° C. and 710 nm/min at 425° C.

[0106] The properties of the TMCTS OSG films after deposition (examples7a and 8a) and after exposure to a UV light source (examples 7b and 8b)are provided in Table IV. The substrate temperature during thedeposition process has a direct effect on the hardness of the TMCTSfilms. Additionally, a lower dielectric constant is obtained with ahigher substrate temperature, indicating clearly that the overall filmproperties of TMCTS-based OSG materials may improve as the temperatureof the substrate is raised. Comparing these same films after UV exposure(examples 7b and 8b), the dielectric constants, mechanical modulus, andhardness are nearly identical. This suggests that the UV exposure stepmay be modifying the chemical structure of the OSG film such that thedirect relationship between dielectric constant and hardness isoptimized. The degree of reorganization required is illustrated by thethickness loss of the film. When the deposition temperature is 350° C.,the film loses 9% thickness upon exposure to UV light; whereas when thedeposition temperature is 425° C. the film thickness decreases by only3%.

[0107] Depending on the application, OSG films used as interlayerdielectric materials can be deposited on a variety of substrates.Because many substrates such as polymeric materials may lose theirmaterial integrity at semiconductor processing temperatures, or forthermal budget reasons, it may be advantageous to expose the OSG film toUV because the exposure can be conducted at relatively lowertemperatures and the dielectric insulating characteristics are retained.The data in Table IV illustrates that an interlayer dielectric materialdeposited at a lower temperatures can be modified by exposure to UVradiation to dramatically improve its overall properties. This change isobtained at modest temperatures and without the addition of chemicalprecursors, and thus, is applicable to a wide variety of applications.TABLE IV Comparison of TMCTS Dense OSG Films deposited at varioustemperatures before and after UV exposure (15 minutes under vacuum).Deposition Thickness Refractive Dielectric Modulus Hardness Ex.Precursor Temperature Loss (%) Index Constant (GPa) (GPa) 7a TMCTS As350° C. N/A 1.385 3.03 6.75 1.10 Dep'd 7b TMCTS UV ″ −9 1.396 2.91 10.491.78 8a TMCTS As 425° C. N/A 1.388 2.86 9.07 1.49 Dep'd 8b TMCTS UV ^(″)−3 1.402 2.93 10.50 1.74

Examples 9 and 10 Formation of a Porous OSG Film Using1-Neohexyl-1,3,5,7-tetramethyl-cyclotetrasiloxane (NH-TMCTS) at VaryingTemperatures

[0108] Organosilicate glass films were formed on silicon wafers viaPECVD of 500 mg/min of the structure/pore former precursor NH-TMCTS withCO₂ as the carrier gas at a flow rate of 200 sccm. The deposition wasperformed at 8 torr, 300 W plasma power, and 300 mils spacing. The wafertemperature during deposition was maintained at either 280° C. (examples9a, 9b, and 9c) or 350° C. (examples 10a, 10b, and 10c). The depositionrate of the film was 625 nm/minute for the films deposited at 280° C.and 420 nm/minute for films deposited at 350° C.

[0109] The properties of the OSG film after deposition (example 9a),after thermal anneal (example 9b), and after exposure to a UV lightsource (example 9c) are provided in Table V. As Table V illustrates,films 9 b and 9 c, which were thermally annealed and exposed to UV lightrespectively, exhibited a change in dielectric constant relative toexample 9a. While film 9 c experienced an increase in dielectricconstant, it also exhibited a significant increase in modulus andhardness, or approximately 91% and 137%, respectively, from example 9a.Example 9b, by contrast, exhibited an decrease in modulus and hardnesscompared with example 9a. Thus, the UV exposure step provides asignificant improvement in the mechanical properties of the OSG glassfilm relative to thermal post-treatment while using milder processingconditions.

[0110] The properties of the OSG film after deposition (Example 10a),after thermal anneal (Example 10b), and after exposure to a UV lightsource (Example 1° C.) are provided in Table V. As Table V illustrates,films 10 b and 10 c, which were thermally annealed and exposed to UVlight respectively, both exhibited a slight increase of 0.06 indielectric constant relative to example 10a. However, film 10 cexhibited a significant increase in modulus and hardness, or anapproximately 57% and 88% increase in hardness, from example 10a.Example 10b, by contrast, exhibited an approximately 4.1% increase inmodulus and approximately 7.8% increase in hardness from example 10a.Thus, the UV exposure step provides a significant improvement in themechanical properties of the OSG glass film relative to thermalpost-treatment while using milder processing conditions. TABLE VComparison of NH-TMCTS Porous OSG Films deposited at varioustemperatures before and after UV exposure (15 minutes under vacuum).Dep. Thickness Refractive Dielectric Modulus Hardness Example PrecursorTemp Loss (%) Index Constant (GPa) (GPa)  9a NH- 280° C. As N/A 1.4062.66 3.09 0.41 TMCTS Deposited  9b NH- 280° C. Thermal −2 1.381 2.542.64 0.35 TMCTS  9c NH- 280° C. UV −14 1.383 2.70 5.90 0.97 TMCTS 10aNH- 350° C. As N/A 1.409 2.63 4.82 0.64 TMCTS Deposited 10b NH- 350° C.Thermal −3 1.400 2.69 5.02 0.69 TMCTS 10c NH- 350° C. UV −6 1.399 2.697.55 1.20 TMCTS

Example 11 Formation of a Porous OSG Film UsingNeohexyl-diethoxymethylsilane (NH-DEMS)

[0111] An organosilicate glass film was formed onto a silicon wafer viaPECVD of 500 mg/min of the structure/pore former precursor NH-DEMS with150 sccm of a helium carrier gas. The deposition was performed at 10torr, 400 W plasma power, and 300 mils spacing. The wafer temperatureduring deposition was maintained at 250° C. The deposition rate of thefilm was 200 nm/minute.

[0112] The properties of the OSG film after deposition (example 11a),after thermal annealing (example 11b), and after exposure to a UV lightsource (example 11c) are provided in Table VI. The dielectric constantof the thermally annealed film decreases by 0.05 or 3%. Likewise, itsmechanical modulus and hardness decrease by 0.62 GPa or 19% and 0.08 GPaor 18%, respectively. Conversely, exposure of the film to a UV lightsource raises each of the dielectric constant by 0.07 or 3%, modulus by10.03 GPa or 305%, and the hardness by 1.97 GPa or 338%. Thus, UVexposure provides for significant enhancement of the mechanicalproperties of the film at milder process conditions and with only asmall increase in the dielectric constant.

Example 12 Formation of a Porous OSG Film UsingNeohexyl-diethoxymethylsilane (NH-DEMS)

[0113] An organosilicate glass film was formed onto a silicon wafer viaPECVD of 500 mg/min of the structure/pore former precursor NH-DEMS with150 sccm of a helium carrier gas. The deposition was performed at 8torr, 500 W plasma power, and 400 mils spacing. The wafer temperatureduring deposition was maintained at 250° C. The deposition rate of thefilm was 240 nm/minute.

[0114] The properties of the OSG film after deposition (example 12a) andafter exposure to a UV light source (example 12b) are provided in TableVI. As Table VI illustrates, the UV post-treatment improved the modulusand hardness of the film by approximately 206% and 236%, respectively,whereas the dielectric constant increased by only 6%. TABLE VIComparison of NH-DEMS Porous OSG Films before and after UV exposure (15minutes under vacuum). Thickness Refractive Dielectric Modulus HardnessExample Precursor Loss (%) Index Constant (GPa) (GPa) 11a NH-DEMS As N/A1.437 2.61 3.29 0.45 Deposited 11b NH-DEMS Thermal −3 1.391 2.56 2.670.37 11c NH-DEMS UV −26 1.385 2.68 13.32 1.97 12a NH-DEMS As N/A 1.4362.70 4.88 0.66 Deposited 12b NH-DEMS UV −23 1.391 2.81 14.93 2.22

Example 13 Formation of a Porous OSG Film Using Diethoxymethylsilane(DEMS), Triethoxysilane (TES), and Alpha-terpinene (ATRP)

[0115] An organosilicate glass film was formed onto a silicon wafer viaPECVD of 210 mg/min of a 50/50 mixture of the structure-formerprecursors DEMS and TES, 490 mg/min of the pore-former ATRP, 200 sccm ofCO₂ and 25 sccm O₂. The deposition was performed at 8 torr, 600 W plasmapower, and 350 mils spacing. The wafer temperature during deposition wasmaintained at 300° C. The deposition rate of the film was 275 nm/minute.

[0116] The properties of the OSG film after deposition (example 13a),after thermal anneal (example 13b), and after exposure to a UV lightsource (example 13c) are provided in Table VII. As Table VIIillustrates, both the thermal and UV post-treatment lowered thedielectric constant. However, the UV post-treatment lowered thedielectric constant by a greater degree, approximately 25% compared tothe thermal post-treatment which lowered the dielectric constant byeapproximately 12%. Further, the UV post-treatment increased the modulusand the hardness of the film by approximately 2% and approximately 10%,respectively, whereas the thermal post-treatment decreased the modulusand the hardness of the film by approximately 41% and 26% respectively.The UV exposure step clearly provides superior properties compared tothe thermal post-treated films at milder conditions.

Example 14 Deposition of Porous OSG Films Using Structure-former1,3-dimethyl-1,3-diethoxy-disiloxane (MEDS) and Pore Formeralpha-terpinene (ATRP)

[0117] An organosilicate glass film was formed onto a silicon wafer viaPECVD of 400 mg/min of the structure-former precursor MEDS, 600 mg/minof the pore-former precursor ATRP with 250 sccm of a CO₂ carrier gas.The deposition was performed at 8 torr, 600 W plasma power, and 350 milsspacing. The wafer temperature during deposition was maintained at 300°C. The deposition rate of the film was 280 nm/minute.

[0118] The properties of the OSG film after deposition (example 14a),after thermal annealing (example 14b), and after exposure to a UV lightsource (example 14c) are provided in Table VII. As Table VIIillustrates, the UV post-treatment increased the hardness of the film byapproximately 46% compared to approximately 1% increase in the thermalannealed film. Further, the UV post-treatment step increased the modulusof the film by approximately 37% whereas the thermal annealingpost-treatment step decreased the modulus by approximately 4%.

[0119]FIG. 3 provides the IR absorption spectrum for each film. As FIG.3 illustrates, at the 1160-1180 nm wavelengths, the absorbanceattributed to Si—O bonding progresses from a double-peak in theas-deposited and thermally annealed films to a single peak with a slightshoulder for the UV-exposed film. This may be attributed to the effectthat the UV exposure has on the network of the porous OSG film. TABLEVII Film Properties for various Porous OSG materials ThicknessRefractive Dielectric Modulus Hardness Example Precursor Loss (%) IndexConstant (GPa) (GPa) 13a DEMS/TES/ATRP As N/A 1.482 3.00 8.17 1.00Deposited 13b DEMS/TES/ATRP Thermal 0 1.351 2.77 5.79 0.74 13cDEMS/TES/ATRP UV −8 1.345 2.51 8.30 1.10 14a MEDS/ATRP As N/A 1.421 2.766.62 1.06 Deposited 14b MEDS/ATRP Thermal 0 1.397 2.72 6.37 1.07 14cMEDS/ATRP UV −7 1.386 2.75 9.08 1.55

Example 15 Deposition of Porous OSG Films Using Diethoxymethylsilane(DEMS) and Alpha-terpinene (ATRP)

[0120] An organosilicate glass film was formed onto a silicon wafer viaPE-CVD of 210 mg/min of the structure-former precursor DEMS, 490 mg/minof the pore-former precursor ATRP, with 200 sccm of a CO₂ carrier gasand 25 sccm of an oxygen additive. The deposition was performed at 8torr, 750 W plasma power, and 350 mils spacing. The wafer temperatureduring deposition was maintained at 300° C. The deposition rate of thefilm was 460 nm/minute.

[0121] The properties of the OSG film after deposition (example 15a),after thermal annealing (example 15b), and after exposure to a UV lightsource (example 15c) are provided in Table VIII. As Table VIIIillustrates, both the thermal and UV post-treatment lower the dielectricconstant but UV exposure lowers the dielectric constant to a greaterdegree. UV exposure improved the modulus and hardness of the filmwhereas thermal annealing decreased the modulus and hardness. Thus, UVexposure clearly provides a superior combination of a lower dielectricconstant and higher hardness compared with the thermally annealed sampleat relatively milder process conditions.

[0122]FIG. 4 provides the UV/visible absorption spectrum of theas-deposited porous DEMS/ATRP film. As FIG. 4 illustrates, this materialhas an appreciable absorption in the region of the spectrum between 190and 280 nm. The structure of the spectrum clearly indicate two distinctmaxima, the first of which is centered at approximately 268 nm, and thesecond at 193 nm. The lower energy absorption is likely from the ATRPpore-former precursor, while the higher intensity and energy absorptionlikely arises from the DEMS network forming precursor.

[0123]FIG. 5 provides the IR absorption spectrum of the as-depositedporous DEMS/ATRP film, Example 15a, as well as that of the film exposedto a UV light source,

Example 15c

[0124] As FIG. 5 illustrates, at the 1160-1180 nm wavelengths, theabsorbance attributed to Si—O bonding progresses from a double-peak inthe as-deposited and thermally annealed films to a single peak with aslight shoulder for the UV-exposed film. This may be attributed to theeffect that the UV exposure has reducing the Si—O bonding associatedwith cage-like structures and introducing a higher degree ofnetwork-like Si—O bonds that are reflected in the increased hardness.TABLE VIII Comparison of Properties of Various Porous OSG Films Beforeand After UV Exposure Thickness Refractive Dielectric Modulus HardnessExample Precursor Loss Index Constant (GPa) (GPa) 15a DEMS/ATRP As N/A1.482 2.98 3.74 0.48 Deposited 15b DEMS/ATRP Thermal   −2% 1.363 2.553.17 0.40 15c DEMS/ATRP UV  −11% 1.345 2.29 4.73 0.57

Examples 16 and 17 Effect of Thermal Treatment Pre- and Post-UV Exposure

[0125] A porous DEMS-based OSG film was deposited by PE-CVD followed bythermal anneal at 425° C. and/or UV exposure. Precursors DEMS (210mg/min), aTRP (490 mg/min), an oxygen additive (25 sccm), and CO₂carrier gases (200 sccm) were introduced into the deposition chamber anddeposited with plasma power of 600W, spacing of 350 mils and a chamberpressure of 8 torr. The wafer temperature was 300° C. The depositionrate was 240 nm/min. The film properties of the as-deposited film(example 16a), thermal annealed film (example 16b), thermal annealedthen UV exposed film (example 16c), and UV exposed film (example 16d)are provided in Table IX.

[0126] A porous DEMS-based OSG film was deposited by PE-CVD followed bythermal anneal at 425° C. and/or UV exposure. Precursors DEMS (210mg/min), aTRP (490 mg/min), an oxygen additive (25 sccm), and CO₂carrier gases (200 sccm) were introduced into the deposition chamber anddeposited with plasma power of 450W, spacing of 350 mils and a chamberpressure of 6 torr. The wafer temperature was 300° C. The depositionrate was 175 nm/min. The film properties of the as-deposited film(example 17a), thermal annealed film (example 17b), thermal annealedthen UV exposed film (example 17c), UV exposed film (example 17d), andUV exposed then thermal annealed film (example 17e) are provided inTable VI.

[0127] Examples 1-15 have shown that UV exposure is superior to thermalannealing for both lowering the dielectric constant and improving thematerial hardness in a single post-treatment processing step for bothdense and porous OSG materials. Examples 16 and 17 illustrate thatthermal annealing and exposure to a UV light source can be used insequence to improve the properties of porous OSG films to an evengreater degree than UV exposure alone. In particular it should be notedthat films subjected to thermal annealing alone, examples 16b and 17b,exhibited a decrease in material hardness by 9% and 11%, respectively,relative to the as-deposited films. On the other hand, the mechanicalhardness of examples 16d and 17d was observed to increase by 5% and 7%,respectively, relative to the as-deposited films. Comparing examples 16bwith 16d and 17b with 17d illustrates again that exposure to UVradiation is a superior method for both increasing the hardness anddecreasing the dielectric constant of porous OSG films.

[0128] Examples 16c and 17c demonstrate that the use of thermalannealing and UV exposure steps in sequence can be used to enhance thematerial properties to an even greater degree than UV exposure alone.The results clearly show that the porous OSG material formed afterthermal annealing is still susceptible to treatment by exposure to UVlight to enhance its materials properties. Conversely, a film exposed toUV light is stable to thermal annealing, as evidenced by the similaritybetween examples 17d and 17e. TABLE IX Comparison of Properties ofVarious Porous OSG Films Before and After UV Exposure ThicknessRefractive Dielectric Modulus Hardness Example Precursor Loss (5%) IndexConstant (GPa) (GPa) 16a DEMS/ATRP As N/A 1.458 2.74 5.87 0.86 Deposited16b DEMS/ATRP Thermal 0 1.350 2.48 4.89 0.74 16c DEMS/ATRP Thermal + −101.354 2.40 7.42 1.07 UV 16d DEMS/ATRP UV −4 1.338 2.44 6.64 0.90 17aDEMS/ATRP As N/A 1. 2.79 4.89 1.05 Deposited 17b DEMS/ATRP Thermal 01.366 2.61 5.87 0.93 17c DEMS/ATRP Thermal + −6 1.348 2.57 3.74 1.55 UV17d DEMS/ATRP UV −3 1.339 2.56 3.17 1.12 17e DEMS/ATRP UV + −4 1.3312.55 4.73 1.03 Thermal

Example 18 Deposition of Porous OSG Films Using Diethoxymethysilane(DEMS) and Alpha-terpinene (ATRP)

[0129] Exemplary porous OSG films were formed onto a silicon wafer viaPE-CVD of 210 mg/min of the structure-former precursor DEMS, 490 mg/minof the pore-former precursor ATRP, with 200 sccm of a CO₂ carrier gasand 25 sccm of an oxygen additive. The deposition was performed at 8torr, 750 W plasma power, 350 mils spacing, and a liquid flow of 675mg/min. The wafer temperature during deposition was maintained at 300°C. The deposition rate of the film was 460 nm/minute.

[0130] The films were exposed to ultraviolet light under either a vacuumatmosphere of about 5 millitorr (example 18a) or under a nitrogenatmosphere having a flow rate of 800 sccm at ambient pressure (example18b). FIGS. 6a and 6 b provide the dielectric constant and refractiveindex versus UV exposure time for examples 18a and 18b, respectively.

[0131]FIGS. 6a and 6 b show that the exposure to UV light removes thepore-former precursor ATRP under either the vacuum or nitrogenatmosphere at ambient pressure within the first couple of minutes ofexposure. This is shown by the drop in both dielectric constant andrefractive index for both exemplary films 18 a and 18 b.

[0132] Examination of the infrared spectra in FIG. 9 shows a dramaticdecrease in the C—H_(x) absorption region near 2900 cm⁻¹ after the firstminute of UV exposure. However, there is noticeably little change inother regions of the spectrum after one minute of UV exposure. Further,there was observed minimal film shrinkage evident during the pore-formerremoval process.

[0133]FIG. 7 and Table X show that the mechanical hardness of the filmdecreased by approximately 10% within the first couple of minutes of UVexposure in a vacuum atmosphere. It was observed that the onset of filmhardening occurs under continued exposure to UV light after 2 minutes,or after removal of the pore-former precursor, and saturates afterapproximately 15 minutes for the lamp power and spectral outputconfiguration.

[0134] Referring to FIGS. 8 and 9, the IR spectra also confirm evidenceof the hardening process shown in FIG. 9 upon removal of the pore-formerprecursor. An evolution of the Si—O region from a double peak to asingle major peak with a shoulder occurs during initial UV exposure. Thetwo areas of the Si—O region (1130 cm⁻¹ and 1060 cm⁻¹) are typical ofcage-like and networked silicate, respectively. Increase in the formermay be characteristic of a silicate doped with terminal groups, whereasincreases in the latter may be more typical of a highly networked oxide.The evolution of the OSG film from a cage-to-network silicate is typicalfor processes that increase the mechanical strength. Further, FIGS. 8and 9 also show decreases in methyl stretching and bending modes as wellas loss of Si—H.

[0135] The chemical composition determined by x-ray photoelectronspectroscopy for an exemplary OSG 18 a films after 1 minute and 15minutes exposure under vacuum are provided in Table XI. The data showsthat the carbon concentration decreases by 48% within the first minuteof UV exposure consistent with the loss of the pore-former precursorfrom the film. However, during the hardening process, there is littlechange in the overall composition of the film despite the 100% increasein hardness and modulus. It is believed that these increases are aresult in a change to the structure of the film. Hydrogen concentration(not shown) may also decrease significantly. Consequently, it isbelieved that the major gas species evolved from UV exposure between 1and 15 minutes are hydrogen-containing species. TABLE X Change in filmproperties for Exemplary OSG film 18a deposited from DEMS and ATRP uponexposure to UV light under vacuum. Time Refractive Dielectric ModulusHardness Thickness (seconds) Index Constant (GPa) (GPa) Loss (%) 0 1.4442.86 6.91 1.01 N/A 15 1.438 2.73 6.79 1.00 0 30 1.358 2.56 5.88 0.91 045 1.344 2.49 6.01 0.96 −1 60 1.344 2.50 6.29 1.02 −2 75 1.344 2.48 7.131.16 −3 90 1.350 2.49 6.29 0.92 −4 105 1.342 2.51 6.59 1.03 −4 120 1.3502.49 8.11 1.27 −4 150 1.347 2.51 7.38 1.16 −4 300 1.363 2.56 9.47 1.52−9 600 1.360 2.62 8.7 1.42 −9 900 1.373 2.64 12.2 1.9 −12.5 1200 1.3802.72 11.8 1.9 −12.5

[0136] TABLE XI Properties of DEMS/ATRP films after UV exposure undervacuum for 1 minute (after generation of porosity) and after 15 minutes(after film hardening). Silicon Oxygen Carbon Formula As-Deposited 30.338.7 31.8 SiO_(1.27)C 1 min. UV 35.3 47.7 17 SiO_(1.34)C_(0.5) 15 min.UV 36.4 50 13.6 SiO_(1.37)C_(0.37)

Example 19 Effect of Atmosphere during UV Exposure on Properties of OSGFilms

[0137] The prior art (US 2003/0054115-A1) provides examples in which UVexposure under oxygen atmosphere is more effective at enhancing themechanical strength of porous HSQ and MSQ films. Furthermore, there wasnegligible negative effect on the dielectric constant when UV exposurewas performed under oxygen. This differs considerably from experimentson dense and porous OSG films deposited from DEMS and DEMS+ATRP.

[0138] An exemplary porous OSG film was formed onto a silicon wafer viaPE-CVD of 173 mg/min of the structure-former precursor DEMS, 402 mg/minof the pore-former precursor ATRP, with 200 sccm of a CO₂ carrier gasand 25 sccm of an oxygen additive. The deposition of the DEMS/ATRP filmwas performed at 8 torr, 750 W plasma power and 350 mils spacing. Thewafer temperature during deposition was maintained at 300° C. Thedeposition rate of the film was 340 nm/minute.

[0139]FIG. 10 and Table XIII illustrates the effect of atmosphere ondielectric constant during UV exposure. The dielectric constant of theas-deposited DEMS/ATRP film was 2.8. The DEMS/ATRP film was subjected toUV exposure for 5 minutes under an air atmosphere to provide a porousDEMS/ATRP film. The dielectric constant of the porous DEMS/ATRP filmafter UV exposure in an air atmosphere was 4.8.

[0140] Dense organosilicate glass films deposited from DEMS ortrimethylsilane were exposed to UV light under differing atmospheres.The dense DEMS film was deposited in a manner similar to the films inexample 6. The dense trimethylsilane film (3MS) was formed onto asilicon wafer via PE-CVD of 600 sccm 3MS and 100 sccm O₂. The depositionof the 3MS films film was performed at 4 torr, 750 W plasma power, and280 mils spacing. The wafer temperature during deposition was maintainedat 350° C. The deposition rate of the film was 600 nm/minute. Thedielectric constant of the 3MS film was 3 and the hardness was 1.3 GPa.The results of UV exposure are provided in Table

[0141] Table XII shows that the dielectric constant increasesdramatically with exposure time for both dense OSG films deposited fromDEMS or for 3MS films. However, the dielectric constant for the 3MS filmremained relatively constant after 600 seconds of exposure to UV lightin a vacuum atmosphere. TABLE XII Change in film properties for denseOSG films when exposed to UV light under air. Time Refractive DielectricThickness Film (seconds) Atmosphere Index Constant Loss (%) DEMS 0 N/A1.429 2.75 N/A DEMS 300 Air 1.421 3.30 0 DEMS 600 ″ 1.423 3.39 0 DEMS1200 ″ 1.419 3.65 0 3MS 0 N/A 1.445 2.95 N/A 3MS 300 Air 1.441 3.65 03MS 600 ″ 1.448 3.90 0 3MS 1200 ″ 1.435 4.45 0 3MS 600 Vacuum 1.439 2.980

[0142] TABLE XIII Change in film properties for porous OSG films whenexposed to UV light under air. Time Refractive Dielectric Thickness Film(seconds) Atmosphere Index Constant Loss (%) DEMS + 0 N/A 1.495 2.86 N/AATRP DEMS + 300 Air 1.525 4.79 −13 ATRP

Example 20 Compositional Uniformity of the DEMS/ATRP OSG Films

[0143] Exemplary porous OSG films were formed onto a silicon wafer viaPE-CVD of 210 mg/min of the structure-former precursor DEMS, 490 mg/minof the pore-former precursor ATRP, with 200 sccm of a CO₂ carrier gasand 25 sccm of oxygen. The deposition was performed at 8 torr, 750 Wplasma power, 350 mils spacing, and a liquid flow of 675 mg/min. Thewafer temperature during deposition was maintained at 300° C. Thedeposition rate of the film was 460 nm/minute.

[0144] Dynamic SIMS depth of profile analysis of the OSG films, asdeposited and after exposure to a UV light source at 1 minute and at 15minutes, was conducted using an cesium ion gun at 2.5 kev to determinethe compositional non-uniformity of the silicon, oxygen, carbon, andhydrogen within each film through detection of negative species atvarious points throughout the thickness of the film. The dynamic SIMSdata is provided in FIGS. 11a through 11 c. The thickness of theas-deposited film, the film exposed to UV light for 1 minute, and thefilm exposed to UV light for 15 minutes was 1 micron, 980 nm, and 890nm, respectively. The percentage of compositional non-uniformity for theOSG film after deposition, after exposure to UV light for 1 minute, andafter exposure to UV light after 15 minutes is provided in FIGS. 11athrough 11 c.

[0145] Table XIV shows that the percentage of compositionalnon-uniformity as calculated using the standard deviation for a varietyof different SIMS measurements taken throughout each film. As FIGS. 11athrough 11 c illustrate, the substantially flat profiles of the silicon,oxygen, carbon, and hydrogen elements contained therein show that thecomposition is substantially uniform throughout the thickness of thefilm. The upward spike in the data at the bottom of the film wasattributable to interfacial effects. TABLE XIV Percentage ofCompositional Non-Uniformity % Uniformity H C O Si As-deposited 3.50643.2662 6.2764 1.6829 After 1 min. UV 1.1669 0.8641 1.2081 1.1438 After15 min. UV 0.9569 0.7892 0.7610 1.0811

Example 21 Deposition of Octamethylcyclotetrasiloxane (OMCTS) Film

[0146] OSG films deposited from plasma enhanced chemical vapordeposition (PE-CVD) of octamethylcyclotetrasiloxane (OMCTS) were exposedto UV light for varying amounts of time. The dielectric constant of thefilm before UV treatment was nominally 3.0. The change in modulus andhardness of the film after UV exposure are provided in Table XV. Thedata shows that UV exposure of an OMCTS film deposited by PE-CVDimproves its material hardness by 83% after exposure and treatment withUV light compared to that of the as-deposited film. TABLE XV Filmproperties after exposure to UV light for the time durations shown. UVExposure Thickness Thickness Dielectric Modulus Hardness Time (minutes)(nm) Loss (%) Constant (GPa) (GPa) 0 930 — 3.0 13.8 2.3 1 920 −1 N/A15.4 2.6 5 870 −6.5 N/A 22.0 3.4 10 860 −7.5 N/A 24.6 3.5 15 850 −8.6N/A 24.4 3.5 30 820 −11.8 N/A 31.3 4.1

[0147] The present invention has been set forth with regard to severalpreferred embodiments, but the scope of the present invention isconsidered to be broader than those embodiments and should beascertained from the claims below.

1. A process for improving a material hardness and an elastic modulus ofan organosilicate film, the process comprising: depositing theorganosilicate film onto at least a portion of a substrate via chemicalvapor deposition of an at least one chemical reagent comprising astructure-former precursor to provide the organosilicate film having afirst material hardness and a first elastic modulus; and exposing theorganosilicate film to an ultraviolet radiation source within anon-oxidizing atmosphere to provide the organosilicate film having asecond material hardness and a second elastic modulus wherein the secondmaterial hardness and the second elastic modulus are at least 10% higherthan the first material hardness and the first elastic modulus.
 2. Theprocess of claim 1 further comprising treating the organosilicate filmwith at least one energy source.
 3. The process of claim 2 wherein thetreating step occurs during at least a portion of the exposing step. 4.The process of claim 2 wherein the at least one energy source heats theorganosilicate film to a temperature between 25 to 450° C.
 5. Theprocess of claim 1 wherein the temperature of the organosilicate filmduring the depositing step ranges from 25 to 450° C.
 6. The process ofclaim 5 wherein the temperature of the organosilicate film during thedepositing step ranges from 250 to 450° C.
 7. The process of claim 1wherein the depositing step involves one or more processes selected fromthe group consisting of thermal chemical vapor deposition, plasmaenhanced chemical vapor deposition, cryogenic chemical vapor deposition,chemical assisted vapor deposition, hot-filament chemical vapordeposition, photo-initiated chemical vapor deposition, and combinationsthereof.
 8. The process of claim 7 wherein the forming step is plasmaenhanced chemical vapor deposition.
 9. The process of claim 1 whereinthe ultraviolet light has one or more wavelengths of about 400 nm orbelow.
 10. The process of claim 1 wherein the ultraviolet light has oneor more wavelengths of about 300 nm or below.
 11. The process of claim 1wherein the ultraviolet light has one or more wavelengths of about 200nm or below.
 12. The process of claim 1 wherein the non-oxidizingatmosphere contains at least one gas selected from the group consistingof nitrogen, hydrogen, carbon monoxide, carbon dioxide, helium, argon,neon, krypton, xenon, radon, and combinations thereof.
 13. The processof claim 1 wherein the non-oxidizing atmosphere comprises a vacuum. 14.The process of claim 13 wherein the pressure ranges from 0.005 millitorrto 5000 torr.
 15. The process of claim 1 wherein the at least onechemical reagent further comprises a pore-former precursor.
 16. Theprocess of claim 15 wherein the dielectric constant of theorganosilicate film after the exposing step is at least 5% less than thedielectric constant of the organosilicate film before the exposing step.17. The organosilicate film prepared by the process of claim
 1. 18. Theorganosilicate film of claim 17 having a compositional non-uniformity ofabout 10% or less.
 19. A method for improving a material hardness and anelastic modulus of a porous organosilicate film deposited by chemicalvapor deposition represented by the formula Si_(v)O_(w)C_(x)H_(y)F_(z),where v+w+x+y+z=100%, v is from 10 to 35 atomic %, w is from 10 to 65atomic %, x is from 5 to 30 atomic %, y is from 10 to 50 atomic %, and zis from 0 to 15 atomic %, the method comprising: providing a substratewithin a vacuum chamber; introducing at least one chemical reagentcomprising a structure-former precursor selected from the groupconsisting of an organosilane and an organosiloxane and a pore-formerprecursor into the vacuum chamber; applying energy to the at least onechemical reagent in the vacuum chamber to induce reaction of the reagentto deposit a composite film comprised of a pore-former material and astructure-former material on at least a portion of the substrate; andexposing the composite film to an ultraviolet light source within anon-oxidizing atmosphere to provide a porous organosilicate film whereinthe material hardness and the elastic modulus of the porousorganosilicate film after the exposing step are higher than the materialhardness and the elastic modulus of the the composite film before theexposing step and wherein the porous organosilicate film issubstantially free of Si—OH bonds.
 20. The method of claim 19 furthercomprising heating the porous organosilicate film wherein the heatingstep is conducted prior to the exposing step.
 21. The method of claim 19wherein the organosilane is at least one member from the groupconsisting of methylsilane, dimethylsilane, trimethylsilane,tetramethylsilane, phenylsilane, methylphenylsilane, cyclohexylsilane,tert-butylsilane, ethylsilane, diethylsilane, tetraethoxysilane,dimethyldiethoxysilane, dimethyldimethoxysilane, dimethylethoxysilane,methyldiethoxysilane, triethoxysilane, methyltriethoxysilane,trimethylphenoxysilane, phenoxysilane, ditertbutylsilane,diethoxysilane, diacetoxymethylsilane, methyltriethoxysilane,di-tert-butylsilane and combinations thereof.
 22. The method of claim 19wherein the organosiloxane is at least one member from the groupconsisting of 1,3,5,7-tetramethylcyclotetrasiloxane,octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane,hexamethyldisiloxane, 1,1,2,2-tetramethyldisiloxane,octamethyltrisiloxane, and combinations thereof.
 23. The method of claim19 wherein the pore-former precursor is at least one member from thegroup consisting of alpha-terpinene, limonene, cyclohexane,1,2,4-trimethylcyclohexane, 1,5-dimethyl-1,5-cyclooctadiene, camphene,adamantane, 1,3-butadiene, substituted dienes, gamma-terpinene,alpha-pinene, beta-pinene, decahydronaphthelene, and combinationsthereof.
 24. The method of claim 19 wherein the pore-former precursorand the structure-former precursor are the same compound.
 25. The methodof claim 24 wherein the compound is at least one member from the groupconsisting of 1-neohexyl-1,3,5,7-tetramethyl-cyclotetrasiloxane,di-neohexyl-diethoxysilane, 1,4-bis(diethoxysilyl)cylcohexane, andcombinations thereof.
 26. The method of claim 19 wherein the substrateis heated during at least a portion of the exposing step.
 27. The methodof claim 19 wherein the applying step is conducted at a temperature ofabout 250° C. or greater.
 28. The organosilicate film prepared by themethod of claim
 19. 29. The organosilicate film of claim 28 having acompositional non-uniformity of about 10% or less.
 30. A mixture fordepositing an organosilicate film comprising a dielectric constant of3.5 or below, the mixture comprising at least one structure-formerprecursor selected from the group consisting of an organosilane and anorganosiloxane and a pore-former precursor wherein at least oneprecursor and/or the organosilicate film exhibits an absorbance in the200 to 400 nm wavelength range.
 31. A mixture for depositing anorganosilicate film, the mixture comprising: from 5 to 95% by weight ofa structure-former precursor selected from the group consisting of anorganosilane and an organosiloxane and from 5 to 95% by weight of apore-former precursor wherein at least one of the precursors and/or theorganosilicate film exhibits an absorbance in the 200 to 400 nmwavelength range.
 32. A process for preparing a porous organosilicatefilm having a dielectric constant of 2.7 or less, the processcomprising: forming a composite film comprising a structure-formermaterial and a pore-former material onto at least a portion of asubstrate wherein the organosilicate film has a first dielectricconstant, a first hardness, and a first elastic modulus; and exposingthe film to at least one ultraviolet light source within a non-oxidizingatmosphere to remove at least a portion of the pore-former materialcontained therein and provide the porous organosilicate film wherein theporous organosilicate film has a second dielectric constant, a secondhardness, and a second elastic modulus and wherein the second dielectricconstant is at least 5% less than the first dielectric constant, thesecond hardness is at least 10% greater than the first hardness, and thesecond elastic modulus is at least 10% greater than the first materialmodulus; and heating the organosilicate film wherein the heating step isconducted prior to the exposing step.
 33. The process of claim 32wherein the forming step is conducted at a temperature of about 250° C.or greater.
 34. The process of claim 32 wherein the organosilicate filmis represented by the formula Si_(v)O_(w)C_(w)H_(y)F_(z), wherev+w+x+y+z=100%, v is from 10 to 35 atomic %, w is from 10 to 65 atomic%, x is from 5 to 30 atomic %, y is from 10 to 50 atomic %, and z isfrom 0 to 15 atomic %.
 35. The process of claim 32 wherein theorganosilicate film has one or more bond types selected from the groupconsisting of silicon-carbon bonds, silicon-oxygen bonds,silicon-hydrogen bonds, and carbon-hydrogen bonds.
 36. The process ofclaim 32 wherein the organosilicate film has a compositionalnon-uniformity of about 10% or less.
 37. An organosilicate film preparedby the process of claim 32.